Optical fiber alignment device with self-healing refractive index-matching gel

ABSTRACT

A fiber alignment device is provided that includes a curable refractive index-matching gel that exhibits self-cleaning and self-healing characteristics upon multiple cycles of insertion and removal of an optical fiber.

CROSS-REFERENCE TO RELATED APPLICATION

This application is being filed on Jun. 6, 2018 as a PCT InternationalPatent Application and claims the benefit of U.S. Patent ApplicationSer. No. 62/515,942, filed on Jun. 6, 2017, the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND

Fiber optic communication systems are becoming prevalent in part becauseservice providers want to deliver high bandwidth communicationcapabilities (e.g., data and voice) to customers. Fiber opticcommunication systems employ a network of fiber optic cables to transmitlarge volumes of data and voice signals over relatively long distances.Optical fiber connectors are an important part of most fiber opticcommunication systems. Fiber optic connectors allow two optical fibersto be quickly optically connected without requiring a splice. Fiberoptic connectors can be used to optically interconnect two lengths ofoptical fiber. Fiber optic connectors can also be used to interconnectlengths of optical fiber to passive and active equipment.

A typical fiber optic connector includes a ferrule assembly supported ata distal end of a connector housing. A spring is used to bias theferrule assembly in a distal direction relative to the connectorhousing. The ferrule functions to support an end portion of at least oneoptical fiber (in the case of a multi-fiber ferrule, the ends ofmultiple fibers are supported). When two fiber optic connectors areinterconnected, the distal end faces of the ferrules abut one anotherand the ferrules are forced proximally relative to their respectiveconnector housings against the bias of their respective springs.

Another type of fiber optic connector can be referred to as aferrule-less fiber optic connector. In a ferrule-less fiber opticconnector, an end portion of an optical fiber corresponding to theferrule-less fiber optic connector is not supported by a ferrule.Instead, the end portion of the optical fiber is a free end portion.Similar to the ferruled connectors described above, fiber optic adapterscan be used to assist in optically coupling together two ferrule-lessfiber optic connectors. Such fiber optic adapters can includespecialized fiber alignment structures adapter to receive bare opticalfibers.

V-grooves are commonly used in prior-art ferrule-less fiber opticalignment devices. An example is the V-groove method described in U.S.Pat. No. 6,516,131 used for alignment of optical fiber ends. TheV-groove is uni-directionally or bi-directionally tapered for enablingeasy positioning of the fibers. Optical fibers are pressed into theV-grooves and line contact between the optical fibers and the surfacesof the V-grooves assists in providing precise alignment of the opticalfibers. In one example, two optical fibers desired to be opticallyconnected together are positioned end-to-end within a V-groove such thatthe V-groove functions to co-axially align the optical fibers. End facesof the aligned optical fibers can abut one another. Other Exampleferrule-less fiber optic connectors are disclosed by PCT Publication No.WO 2012/112344; PCT Publication No. WO 2013/117598 and U.S. Pat. No.8,870,466.

For optical couplings to be effective, it is important for the end facesof the optical fiber being coupled together to be clean. Improvementsare needed in this area.

Air gaps between glass fibers in optical fiber network connectors causeproblems because the refractive index of air is lower than therefractive index of glass. Refractive index-matching gels are employedto displace air gaps and reduce signal loss or reflection within theoptical fiber networks and protect the optical interface from theenvironment. Index matching agents range from fluids, to pastes, togreases, to gels. Thixotropic greases and gels have the ability to staywhere they are placed, which is important for certain applications. Gelsfurther bring a cross-linked structure memory, which may improveself-healing or re-sealing characteristics.

Prior art index-matching gels such as thixotropic greases or crosslinkedcured gels may exhibit good index match to the glass fiber, high opticalclarity, and low absorption loss; however upon repeated removal andreplacement of optical fibers, existing gels may exhibit tracking, ortear-out, wherein the gel adheres to the optical fiber.

U.S. Pat. No. 4,634,216, incorporated herein by reference in itsentirety, discloses index matching silicon gels preferably withsufficiently low hardness to allow the fiber end sections to be easilyintroduced and positioned. The gel preferably exhibits self-cleaning.Should any dust inadvertently collect on the endface of a fiber beforeinsertion in a housing or connector, the gel through its adhesivecapacity wipes off the fiber end section, as it is inserted into thehousing and thus into the gel, thereby gathering the dust. No specificformulations are provided.

U.S. Pat. No. 4,777,063, incorporated herein by reference in itsentirety, discloses curable organopolysiloxane compositions comprisingat least about 50% by weight of a general organopolysiloxane having nomore than two vinyl groups and up to about 50% by weight of a crosslinkadditive which is a polysiloxane having at least 3 vinyl groups andwhich is copolymerizable with the organopolysiloxane. This curablecomposition may be cured by heat, chemical or, preferably, radiationcuring techniques to produce crosslinked polysiloxane materials.

U.S. Pat. No. 5,079,300, incorporated herein by reference in itsentirety, discloses cured crosslinked organopolysiloxane compositions,for example, using two component reactive silicone compositions employedin various ratios to obtain different hardness characteristics.Materials comprising first and second components contain vinyl groupsand silicon bonded hydrogen atoms, for example, with use of a platinumcatalyst to facilitate reaction and cure.

U.S. Pat. No. 5,783,115, incorporated herein by reference in itsentirety, discloses index-matching gel compositions that are opticallytransmissive, silica-containing compositions which exhibit a smallchange of refractive index with respect to changes in temperature(dn_(g)/dT). The compositions are derived from silica sols dispersed inliquid organic polymers. In one example, a transparent crosslinkable solcontaining silica was prepared by mixing silica organosol A into atetrahydrofuran solution of an epoxy resin.

US 2009/0087150, incorporated herein by reference in its entirety,discloses a polymer based index-matching gel preferably within aviscosity at 25° C. of 3 Pa-s to 100 Pa-s, although no specificformulations are provided.

Prior art commercial cross-linked gels such as NYOGEL® OCK-451A (NyeLubricants, Inc., Fairhaven Mass.) can achieve index match, and re-seal,but one problem is they may start to exhibit tear-out after a number ofcycles. For example, as shown in FIG. 14, prior art cross-linked gelexhibits tear-out as evidenced by traces of gel visually apparent alongthe withdrawn optical fiber.

Prior art commercial thixotropic greases such as NYOGEL® OC431A LVP canexhibit good index-match, with good fiber release, but may exhibitanother problem in that they fail to self-heal as exhibited by trackingor passage evident after a number of cycles. For example, as shown inFIG. 15, prior art thixotropic grease exhibits tracking after withdrawalof the optical fiber, thus fails to adequately self-heal.

Thus, one problem to be solved is to provide a gel that exhibits goodprotection of substrates such as optical fiber interfaces from theenvironment, good index-match to optical fibers, self-cleaningproperties, and further exhibits self-healing properties withoutexhibiting tear-out along a withdrawn optical fiber, particularly afterseveral cycles.

SUMMARY

A fiber alignment device includes a curable refractive index-matchinggel that exhibits self-cleaning and self-healing characteristics uponmultiple cycles of insertion and removal of an optical fiber. Refractiveindex-matching self-curing gels are provided to displace air gaps andreduce signal loss or reflection within the optical fiber networks andprotect the optical interface from the environment.

Cured organopolysiloxane gel compositions are provided havingunexpectedly superior combinations of elongation, tensile strength, andtoughness, accepting high levels of diluent without significantsyneresis, particularly while under compression, while maintainingindex-matching, self-curing and self-cleaning characteristics.

In some embodiments, a cured refractive index-matching gel compositionis provided comprising a crosslinked polysiloxane, and a nonreactivepolysiloxane diluent, wherein the refractive index of the diluent ishigher than the refractive index of the crosslinked polysiloxane.

In some embodiments, a cured refractive index-matching gel compositionis provided, wherein the gel composition is self-healing as indicated byre-seal to be liquid tight upon water submersion after at least 10seconds following removal of a 125 micron optical fiber from the gelcomposition within a connector.

In some embodiments, a cured refractive index-matching gel compositionis provided, wherein the crosslinked polysiloxane is prepared from apolysiloxane composition comprising a first reactive polysiloxanecomponent, and a second reactive component capable of reacting with andcuring the first component, wherein the first reactive polysiloxanecomponent has at least two reactive groups. In some embodiments, thefirst reactive polysiloxane component is selected from the groupconsisting of hydroxy-, alkoxy-, acyloxy-, amino-, oxime-, hydrogen- andvinyl-dimethyl terminated polydimethylsiloxanes, and dihydroxy-,diacyloxy-, diamino-, dioxime-, dialkoxy-, dihydrogen- anddivinyl-methyl terminated polydimethylsiloxanes and hydroxy-, alkoxy-,acyloxy-, amino-, oxime-, hydrogen- and vinyl-dimethyl and dihydroxy-,diacyloxy-, diamino-, dioxime-, dialkoxy-, dihydrogen- anddivinyl-methyl terminated dimethylsiloxane copolymers with diphenylsiloxanes.

In some embodiments, a cured refractive index-matching gel compositionis provided, wherein the crosslinked polysiloxane is prepared from apolysiloxane composition comprising a first reactive polysiloxanecomponent, and a second reactive component capable of reacting with andcuring the first component wherein the second reactive component has atleast three reactive groups, for example, wherein the second reactivecomponent is selected from the group consisting oftetrakis(dimethylsiloxy) silane, methyltris(dimethylsiloxy)silane,phenyl-tris(dimethylsiloxy)silane, tetraethoxysilane,tetramethoxysilane, phenyl triethoxysilane, methyl triethoxysilane,phenyl triacetoxysilane, 1,3,5-trimethyltrivinyl cyclotrisiloxane,1,3,5,7-tetramethyltetravinyl cyclotetrasiloxane, and1,3,5,7-tetra-methylcyclotetrasiloxane. In some embodiments, the secondreactive component has at least four reactive groups. In someembodiments, a mixture of second reactive components comprising 3 and 4reactive groups is employed to control Mw between crosslinks.

In some embodiments, a cured refractive index-matching gel compositionis provided comprising a crosslinked polysiloxane, and a nonreactivepolysiloxane diluent, wherein the nonreactive polysiloxane diluentcomprises a cyclosiloxane having at least one phenyl substituent.

In some embodiments, a cured refractive index-matching gel compositionis provided comprising a crosslinked polysiloxane, and a nonreactivepolysiloxane diluent, wherein the nonreactive polysiloxane diluent is acyclosiloxane selected from the group consisting of a diphenylcyclotrisiloxane (D3), triphenyl cyclotrisiloxane (D3), diphenylcyclotetrasiloxane (D4), tetraphenyl cyclotetrasiloxane (D4), hexaphenylcyclotetrasiloxane (D4), diphenyl cyclopentasiloxane (D5), tetraphenylcyclopentasiloxane (D5), hexaphenyl cyclopentasiloxane (D5), diphenylcyclohexasiloxane (D6), tetraphenyl cyclohexasiloxane (D6), hexaphenylcyclohexasiloxane (D6), diphenyl cycloheptasiloxane (D7), tetraphenylcycloheptasiloxane(D7), and hexaphenyl cycloheptasiloxane(D7). In someembodiments, a cured refractive index-matching polymer gel is provided,wherein the crosslinked polysiloxane has an average molecular weightbetween crosslinks of at least 15,000, or at least 20,000.

In some embodiments, a cured refractive index-matching gel compositionis provided comprising a crosslinked polysiloxane, and a nonreactivepolysiloxane diluent, wherein the composition comprises 40% up to about90% by weight of the nonreactive polysiloxane diluent based on thecombined weights of the crosslinked polysiloxane and the nonreactivepolysiloxane diluent.

In some embodiments, the polysiloxane composition further comprises oneor more additives selected from the group consisting of catalysts,antioxidants, moisture scavengers, antimicrobials, flame retardants,corrosion inhibitors, UV light stabilizers, fungicides, cure inhibitors,tackifiers, and nanoparticles.

In some embodiments, a cured refractive index-matching gel compositionis provided comprising amorphous silica particles having mean diameterin the range of from 1 nm to no more than 500 nm.

In some embodiments, a cured refractive index-matching gel compositionis provided, wherein the composition exhibits

i. a hardness as measured by a texture analyzer is in the range of from1 g to 525 g;

ii. an ultimate elongation of at least about 100%; and

iii. a refractive index in the range of from 1.31 to 1.60 at 1550 nm byASTM D-1218.

In some embodiments, a cured refractive index-matching gel compositionis provided, wherein the composition exhibits

i. a hardness as measured by a texture analyzer is in the range of from5 to 40 g;

ii. an ultimate elongation of at least about 400%; and

iii. a refractive index in the range of from 1.40 to 1.48 at 1550 nm byASTM D-1218.

A cured refractive index-matching polymer gel composition is providedcomprising a crosslinked polymer, and a optionally a nonreactivediluent, wherein the refractive index of the diluent is higher than therefractive index of the crosslinked polymer.

An index-matching gel composition is provided prepared from acomposition comprising two parts.

Discrete product applications may require a differing levels of“self-healing” and “self-cleaning” characteristic, depending upongeometry, fiber diameter, gel reservoir geometry, and environment. Ourability to tune these properties by adjusting the Part A to Part B ratiois beneficial.

A cured polysiloxane polymer gel, and an optical fiber alignment systemcontaining a cured polysiloxane gel, is provided comprising acrosslinked polysiloxane polymer, wherein the crosslinked polysiloxanepolymer is prepared from a two-part composition comprising a part A anda part B, wherein part A and part B are mixed in a ratio of from 2:1 to1:2; 1.5:1 to 1:1.5, 1.1:1 to 1:1.1, or 1.05:1 to 1:1.05 of part A:partB; and wherein the cured polysiloxane polymer gel does not exhibittracking or tear-out of the gel for at least 6, at least 8 or at least12 cycles after inserting and withdrawing an optical fiber from thecured gel. One of Part A and Part B may contain a divinyl terminatedPDMS and a platinum catalyst, and the other may contain a dihydrideterminated PDMS and a second reactive component having at least threereactive groups, or at least four reactive groups. The second reactivecomponent may have at least three reactive hydride groups, or at leastfour reactive hydride groups. One or both of Part A or Part B maycontain a non-reactive polysiloxane diluent.

The combined two parts may include a nonreactive diluent comprising acyclosiloxane and optionally a trimethyl terminatedpolydimethylsiloxane, an organopolysiloxane comprising a vinyl dimethylterminated polydimethylsiloxane, a dimethylsiloxane compound comprisingat least 3 or at least 4 Si—H hydride functional groups, a PlatinumCatalyst; and optionally a cure inhibitor. In some embodiments, the cureinhibitor is 1,3,5,7-Tetravinyltetramethylcyclotetrasiloxane (UCTSpecialties T 2160).

In some embodiments, an index-matching gel composition is provided thatis prepared from a two part composition, the first part comprising anonreactive diluent comprising a diphenyl or tetraphenyl cyclosiloxane,a vinyldimethyl terminated polydimethylsiloxane having two vinyl groups,and a platinum catalyst; and the second part comprising a nonreactivediluent comprising a diphenyl or tetraphenyl cyclosiloxane, and adimethylsiloxane compound dimethylsiloxane compound comprising at least3 or at least 4 Si—H hydride functional groups.

Discrete product applications may require a differing levels of“self-healing” and “self-cleaning” characteristic, depending upongeometry, fiber diameter, gel reservoir geometry, and environment. Theability to tune these properties by adjusting the Part A to Part B ratiois beneficial. Refractive-index may be adjusted by adding a non-reactivepolysiloxane diluent having a higher refractive index than the cured gelwithout diluent.

In some embodiments, an optical fiber alignment system is providedcomprising: an alignment device defining a fiber insertion axisextending between first and second ends of the alignment device, thealignment device also defining a fiber alignment region positioned alongthe fiber insertion axis; and a cured refractive index-matching gelcomposition positioned within the fiber alignment region, wherein anoptical fiber to be aligned penetrates through the gel, wherein thecured refractive index-matching gel composition comprises a crosslinkedpolysiloxane, and a nonreactive polysiloxane diluent, wherein therefractive index of the diluent is higher than the refractive index ofthe crosslinked polysiloxane.

In some embodiments, a method for preparing a crosslinkedorganopolysiloxane gel is provided which comprises reacting together: 1)a organopolysiloxane containing first reactive groups; and 2) at leastone compound containing second reactive groups, wherein said secondreactive groups in the compound being capable of reacting with saidfirst reactive groups in the organopolysiloxane; in the presence of adiluent, which is inert to said first and said second reactive groups,in an amount of from at least about 40% by weight to about 95% by weightof the combined weights of said diluent, said organopolysiloxane andsaid compound, wherein the inert diluent is a cyclopolysiloxane having arefractive index higher than the organopolysiloxane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal, cross-sectional view of a fiber optic adapterincorporating an example fiber alignment device in accordance with theprinciples of the present disclosure; the fiber optic adapter is shownreceiving and optically coupling together two ferrule-less fiber opticconnectors;

FIG. 2 is a front, top, left side perspective view of the fiberalignment device of FIG. 1;

FIG. 3 is a rear, bottom, right side view of the fiber alignment deviceof FIG. 2;

FIG. 4 is an exploded, top view of the fiber alignment device of FIG. 2;

FIG. 5 is a cross-sectional view taken along section line 5-5 of FIG. 4;

FIG. 6 is a perspective, exploded view of the fiber alignment device ofFIG. 2;

FIG. 7 is another perspective, exploded view of the fiber alignmentdevice of FIG. 1;

FIG. 8 is a cross-sectional view of the fiber alignment device of FIG. 2taken along the fiber insertion axis;

FIG. 9 is a cross-sectional view of the fiber alignment device of FIG. 2taken along an axis transverse to the fiber insertion axis;

FIG. 10 is a bottom view of an example fiber alignment component of thefiber alignment device of FIG. 4;

FIG. 11 is a perspective view of another fiber alignment device inaccordance with the principles of the present disclosure; the fiberalignment device is shown receiving and optically coupling together twogroups of optical fibers;

FIG. 12 is a top view of a top portion of the self-centering device ofFIG. 11; and

FIG. 13 is a top view of a bottom portion of the self-centering deviceof FIG. 11.

FIG. 14 is a photograph of a prior art cross-linked gel that achievesindex-match and reseal, but exhibits gel tear-out after 4^(th) insertionof the optical fiber.

FIG. 15 is a photograph of a prior art thixotropic grease that achievesindex match with good fiber release, but tracks after 6^(th) insertionof the optical fiber, as evident by residual hole after withdrawal ofoptical fiber.

FIG. 16 shows a photograph of prior art thixotropic grease placedbetween two glass slides exhibiting tracking after withdrawal of opticalfiber.

FIG. 17A shows cured gel of example 6 using a Part A:Part B ratio of1.00:1.04 immediately after withdrawal of optical fiber. No tracking ortear-out of the gel is observed, but a dimple is temporarily observed atthe exit point.

FIG. 17B shows cured gel of example 6 using a Part A:Part B ratio of1.04:1.00 immediately after withdrawal of optical fiber. No tracking ortear-out of the gel is observed, but a dimple is temporarily observed atthe exit point. Some draw-out is observed that snaps back to gel matrixwithin 2-3 seconds.

FIG. 17C shows cured gel of example 6 using a Part A:Part B ratio of1.06:1.00 immediately after withdrawal of optical fiber. No tracking ortear-out of the gel is observed, but a dimple is temporarily observed atthe exit point. Some draw-out is observed that snaps back to gel matrixwithin 10-12 seconds.

FIG. 18A shows initial image of dust coated optical fiber prior toinsertion to cured gel according to example 6.

FIG. 18B shows image of dust coated optical fiber after insertion andremoval from self-cleaning cured gel according to example 6.

FIG. 18C shows initial image of dust coated optical fiber prior toinsertion to prior art gel grease.

FIG. 18D shows image of dust coated optical fiber after insertion andremoval from prior art gel grease where dust still appears on opticalfiber.

DETAILED DESCRIPTION

Various examples will be described in detail with reference to thedrawings, wherein like reference numerals represent like parts andassemblies throughout the several views. Any examples set forth in thisdisclosure are not intended to be limiting and merely set forth some ofthe many possible ways for implementing the broad inventive aspectsdisclosed herein. In this description, words such as “upper,” “top,”“lower,” and “bottom” have been used for ease of description to describethe positional relationships of the various features, parts andcomponents. It will be appreciated that such terms are not intended tobe construed as limiting. For example, such terms are not intended tomean that a fiber alignment device in accordance with the principles ofthe present disclosure is required to be used in a particularorientation. For example, in actual use, a feature identified herein asbeing a top feature can be installed in a bottom orientation and afeature described herein as being a bottom feature could be installed ina top orientation.

All patents, patent applications and publications referred to herein areincorporated by reference in their entirety.

The term “about,” as used herein when referring to a measurable valuesuch as an amount of a compound, dose, time, temperature, and the like,is meant to encompass variations of 10%, 5%, 1%, 0.5%, or even 0.1% ofthe specified amount.

The disclosure is directed to a fiber alignment device for axiallyaligning and coupling optical fibers such that optical signals can betransferred from one of the optical fibers to the other. Gel of the typedescribed herein can be disposed within the fiber alignment device toaid in optically coupling and/or cleaning the optical fibers. In certainimplementations, the optical fibers are supported by ferrule-lessoptical connectors. The fiber alignment device can include groovesformed in substrates, v-grooves, micro-alignment bores, spring-biasedballs, cantilever structures, and/or other alignment mechanisms toaxially align the optical fibers.

In some implementations, a fiber alignment device has a front and arear. The fiber alignment device is configured to receive a singleoptical fiber at the front and a single optical fiber at the rear. Thefiber alignment device axially aligns and optically couples the opticalfiber received at the front and the optical fiber received at the rear.In other implementations, the fiber alignment device is configured toreceive multiple optical fibers (e.g., a ribbon cable) at the front andmultiple fibers at the rear. The fiber alignment device axially alignsand optically couples the plurality of optical fibers received at thefront and the plurality of optical fibers received at the rear.

Example ferrule-less connectors suitable for use with the fiberalignment devices disclosed herein are described in U.S. Pat. No.9,575,263 (hereinafter “the '263 patent”), the disclosure of which ishereby incorporated herein by reference. The '263 patent also disclosesexample fiber alignment devices suitable for holding the gel describedherein. Other suitable fiber alignment devices are disclosed in U.S.application Ser. No. 15/512,301, filed Mar. 17, 2017, and titled“Optical Fiber Connection System Including Optical Fiber AlignmentDevice;” U.S. Application No. 62/454,439, filed Feb. 3, 2017, and titled“Device for Aligning Optical Fibers;” and U.S. Application No.62/430,343, filed Dec. 5, 2016, and titled “Multi-Fiber Ferrule-lessDuplex Fiber Optic Connectors with Multi-Fiber Alignment Devices,” thedisclosures of which are hereby incorporated herein by reference.

Referring to the figures in general, example ferrule-less fiberalignment devices suitable to hold the gel disclosed herein are shown.FIGS. 1-9 illustrate an alignment device suitable for optically couplingtogether two optical fibers (e.g., two ferrule-less optical connectors).FIG. 10 illustrates an alignment device suitable for optically couplinga plurality of optical fibers to another plurality of optical fibers.

FIGS. 1-9 illustrate a fiber alignment device 20 in accordance with theprinciples of the present disclosure. The fiber alignment device 20 isadapted for co-axially aligning optical fibers such that the opticalfibers are optically coupled so that light can be transferred from onefiber to the other.

While the embodiment disclosed herein is configured to align two opticalfibers, it will be appreciated that the various parts and componentscould be duplicated so as to be applicable to alignment devices foraligning multiple sets of optical fibers.

Additionally, it will be appreciated that fiber alignment devices inaccordance with the principles of the present disclosure can be used foraligning optical fibers in a variety of applications. For example,alignment devices in accordance with the principles of the presentdisclosure can be incorporated within fiber optic adapters that areconfigured for receiving ferrule-less fiber optic connectors. In such ause, the alignment devices are configured for aligning ferrule-lessoptical fibers corresponding to the fiber optic connectors when thefiber optic connectors are inserted within ports of the fiber opticadapters. In other examples, fiber alignment devices in accordance withthe principles of the present disclosure can be incorporated withinconnectors such as field-installable connectors to provide opticalcouplings within the connectors. Moreover, fiber alignment devices inaccordance with the principles of the present disclosure can be used atsplice trays, or other locations where it is desired to providemechanical splicing between optical fibers.

FIG. 1 shows the fiber alignment device 20 incorporated within a fiberoptic adapter 22. The fiber optic adapter 22 includes adapter ports 24a, 24 b for receiving fiber optic connectors such as ferrule-less fiberoptic connectors 26 a, 26 b. The ferrule-less fiber optic connectors 26a, 26 b include optical fibers 28 having free-end portions 30 that arenot supported by structures such as ferrules (i.e., relatively hardstructures which typically support the ends of optical fibers intraditional ferruled connectors such as SC-connectors, LC-connectors,MPO connectors and other types of connectors). In certain examples, thefree-end portions 30 are bare fibers which typically include a coresurrounded by only a cladding layer. In other examples, the free-endportions 30 may include one or more coatings. As shown at FIG. 1, theferrule-less fiber optic connectors 26 a, 26 b are respectively receivedin the adapter ports 24 a, 24 b and the free-end portions 30 of theircorresponding optical fibers 28 are received within the fiber alignmentdevice 20. The fiber alignment device 20 is centrally located within thefiber optic adapter 22 and receives and coaxially aligns the free-endportions 30 of the ferrule-less fiber optic connectors 26 a, 26 b whenthe ferrule-less fiber optic connectors 26 a, 26 b are inserted withintheir corresponding adapter ports 24 a, 24 b.

Referring to FIGS. 4-7, the fiber alignment device 20 includes an outerfiber alignment housing 40 configured to contain a fiber alignmentsubassembly 42. The fiber alignment subassembly 42 includes a fiberengagement component 44 and a guide feature 46 defining a fiberalignment groove 48 (see FIG. 9). The fiber engagement component 44 caninclude a plastic or polymeric structure (e.g., a molded plastic part)which can include a main body 50 defining a top side 52 and a bottomside 54 (see FIG. 5).

The fiber engagement component 44 can also include elastic cantileverarms 56 a, 56 b. In one example, the elastic cantilever arms 56 a, 56 bare unitarily formed as one piece with the main body 50 of the fiberengagement component 44. For example, the elastic cantilever arms 56 a,56 b can include base ends 58 a, 58 b that are monolithically connectedwith the main body 50. The bottom side 54 of the main body 50 can definean elongate pocket 60 that is open in a downwardly facing direction. Theguide feature 46 can include parallel rods 62 a, 62 b that fit withinthe elongate pocket 60 and that cooperate to define the fiber alignmentgroove 48. When the fiber alignment subassembly 42 is installed withinthe fiber alignment housing 40, the fiber alignment housing 40 includesstructure that forces, compresses or otherwise retains/holds the rods 62a, 62 b in the elongate pocket 60 such that the fiber alignment housing40 assists in positioning and retaining the rods 62 a, 62 b within theopen sided elongate pocket 60.

Referring back to FIGS. 2-3, the fiber alignment housing 40 includesfirst and second housing pieces 64 a, 64 b that meet at a centralinterface plane. In certain examples, the first and second housingpieces 64 a, 64 b can be half-pieces. The first and second housingpieces 64 a, 64 b respectively define opposite first and second ends 68a, 68 b of the fiber alignment housing 40. The opposite first and secondends 68 a, 68 b define co-axially aligned first and second fiberinsertion openings 70 a, 70 b that are aligned along a fiber insertionaxis 72 that is oriented generally perpendicular relative to the centralinterface plane 66. The first and second housing pieces 64 a, 64 binclude flange portions 74 a, 74 b that cooperate to define a centralflange 74 of the fiber alignment housing 40. Opposing axial end faces 75a, 75 b of the flange portions 74 a, 74 b mate at the central interfaceplane 66. The axial end faces of the flange portions 74 a, 74 b caninclude male projections 90 that fit within corresponding femalereceptacles 92.

The first and second housing pieces 64 a, 64 b also includebarrel-portions 76 a, 76 b that project axially outwardly from theflange portions 74 a, 74 b along the fiber insertion axis 72. Thebarrel-portions 76 a, 76 b include axial end faces 78 a, 78 b. The fiberinsertion openings 70 a, 70 b are defined through the axial end faces 78a, 78 b. The axial end faces 78 a, 78 b also include transition portions80 a, 80 b that surround the fiber insertion openings 70 a, 70 b.Transition portions 80 a, 80 b can be configured for guiding ordirecting optical fibers into the fiber insertion openings 70 a, 70 b.In certain examples, the transition portions 80 a, 80 b can be taperedor angled relative to the fiber insertion axis 72. In certain examples,the transition portions 80 a, 80 b can be funnel-shaped

When the fiber alignment device 20 is assembled (see FIGS. 2 and 3), thefiber alignment groove 48 preferably generally aligns with the fiberinsertion axis 72 in a coaxial orientation. Additionally, the elasticcantilever arms 56 a, 56 b of the fiber engagement component 44 havinglengths that extend along (e.g., parallel to and above) the fiberalignment groove 48 as well as the fiber insertion axis 72. The elasticcantilever arms 56 a, 56 b are provided within recesses 82 a, 82 bdefined through the top side 52 of the main body 50 of the fiberengagement component 44. The recesses 82 a, 82 b as well as the elasticcantilever arms 56 a, 56 b are separated by an intermediate cross-rib 84that provides transverse reinforcement to the fiber engagement component44. The cross-rib 84 is centrally located between opposite ends 86 a, 86b of the main body 50 of the fiber engagement component 44. Thecantilever arms 56 a, 56 b include free ends 88 a, 88 b adjacent thecross-rib 84 and base ends 58 a, 58 b generally adjacent to thecorresponding opposite ends 86 a, 86 b of the main body 50. Taperedfiber insertion transitions 87 a, 87 b are provided at the ends 86 a, 86b for guiding fibers into the fiber alignment groove 48.

In certain examples, the parallel rods 62 a, 62 b can be cylindrical. Incertain examples, the parallel rods 62 a, 62 b can have rounded ends. Incertain examples, rounded ends can be dome or semi-spherically shaped.In certain examples, the rounded ends can be configured to guide ordirect optical fibers into the fiber alignment groove 48.

The fiber alignment subassembly 42 can include features that ensureprecise relative positioning between the fiber engagement component 44and the guide feature 46. In certain examples, the fiber alignmentsubassembly 42 can have structures that precisely position the rods 62a, 62 b relative to the main body 50 of the fiber engagement component44, and can also include structures that ensure that the free ends 88 a,88 b of the elastic cantilever arms 56 a, 56 b are positioned at apredetermined spacing from the fiber alignment groove 48. Thepredetermined spacing can be configured such that fibers can be readilyreceived within the fiber alignment groove 48 without experiencing undueresistance from the elastic cantilever arms 56. Simultaneously, thecantilever arms 56 are positioned close enough to the fiber alignmentgroove 48 to apply sufficient pressure to the optical fibers receivedwithin the fiber alignment groove 48 such that the optical fibers areheld and retained within the fiber alignment groove 48 in coaxialalignment with one another.

In certain examples, the free ends 88 a, 88 b of the cantilever arms 56a, 56 b can have a preferred configuration that provides the dualfunction of contacting optical fibers inserted within the fiberalignment groove 48, and contacting the rods 62 a, 62 b for causing thecantilever arms 56 to flex relative to the main body 50 to a stagedposition in which a desired spacing is provided between fiber contactregions of the elastic cantilever arms 56 and the fiber alignment groove48. In certain examples, the free ends 88 a, 88 b can include central,downwardly projecting tab portions 96 a, 96 b that align with the fiberalignment groove 48. In certain examples, the tab portions 96 a, 96 bare positioned directly above the fiber alignment groove 48. In certainexamples, the tab portions 96 a, 96 b project from main bodies of theelastic cantilever arms 56 a, 56 b so as to project closer to the fiberalignment groove 48 such that a predefined fiber contact spacing isdefined by the tab portions 96 a, 96 b. In certain examples, the tabportions 96 a, 96 b are the only portions of the cantilever arms 56 a,56 b that contact the optical fibers when the optical fibers are withinthe fiber alignment grooves 48.

The free ends 88 a, 88 b also include wing portions 98 a, 98 b thatproject laterally outwardly from opposite sides of the tab portions 96a, 96 b. The wing portions 98 a, 98 b are elevated or otherwise offsetfrom the tab portions 96 a, 96 b so that the wing portions 98 a, 98 bare not adapted to contact the optical fibers within the fiber alignmentgroove 48. Instead, the wing portions 98 a, 98 b include referencesurfaces 100 a, 100 b that contact top sides of the rods 62 a, 62 b (seeFIGS. 8 and 9) to cause the elastic cantilever arms 56 to flex relativeto the main body 50 of the fiber engagement component 44 to a positionwhere the tab portions 96 a, 96 b are spaced a predetermined andprecisely controlled amount from the fiber alignment groove 48 when therods 62 a, 62 b are pressed in the pocket of the main body 50.

The free ends 88 a, 88 b can be described as having a hammerheadconfiguration. The wing portions 98 a, 98 b can rest on the rods 62 a,62 b (e.g., the tops of the rods) prior to insertion of the opticalfibers along the fiber insertion axis 72. The rods can be sized suchthat the optical fibers are level or almost exactly level with the topsof the rods (horizontal tangent to the tops of the fibers are tangentwith the tops of the rods). The size (e.g., projection depth) of the tabportions 76 a, 76 b control the amount of friction/interferencegenerated as the fibers are inserted along the alignment groove. Byvarying the size of the rods and/or the depth the tabs portions 76 a, 76b project, the amount of interference during insertion of the opticalfibers into the alignment device and thus the required insertion forcecan be varied/controlled.

The fiber alignment subassembly 42 also includes structure for ensuringthat the guide feature 46, such as the rod 62 a, 62 b, are positioned ata precise location relative to the main body 50 of the fiber engagementcomponent 44. In one example, the main body 50 of the fiber engagementcomponent 44 can include a reference surface arrangement within theelongate pocket including reference surfaces 102 a, 102 b (see FIG. 8)against which the rods 62 a, 62 b are pressed when the fiber alignmentsubassembly 42 is loaded within the fiber alignment housing 40.

In certain examples, the reference surfaces 102 a, 102 b are locatedgenerally adjacent the base ends 58 a, 58 b of the elastic cantileverarms 56 a, 56 b. In certain examples, the reference surfaces 102 a, 102b engage top portions of the rods 62 a, 62 b when the rods are pressedinto the pocket by the housing 40. In certain examples, the referencesurfaces 102 a, 102 b engage first portions of the top sides of theparallel rods 62 a, 62 b and the reference surfaces 100 a, 100 b of thewing portions 98 a, 98 b engage second portions of the top sides of theparallel rods 62 a, 62 b. In certain examples, reference surfaces 100 a,100 b and the reference surfaces 102 a, 102 b engage the same sides ofthe rods 62 a, 62 b (e.g., the reference surfaces all engage the topsides of the rods 62 a, 62 b). In this way, the reference surfaces 100a, 100 b, and the reference surfaces 102 a, 102 b cooperate to ensurethat the tab portions 96 a, 96 b of the cantilever arms 56 a, 56 b arepositioned at a desired spacing relative to the fiber alignment groove48. The reference surfaces 102 a, 102 b establish precise positioningbetween the main body 50 of the fiber engagement component 44 and theparallel rods 62 a, 62 b; and the reference surfaces 100 a, 100 bestablish precise positioning between the tab portions 96 a, 96 b of thecantilever arms 56 a, 56 b and the rods 62 a, 62 b.

The reference surfaces 102 a, 102 b are part of the main body 50 of thefiber engagement component 44 and are preferably mechanically decoupled(mechanically isolated) from the cantilever arms 56 a, 56 b. Thus,contact and loading between the rods 62 a, 62 b and the referencesurfaces 102 a, 102 b does not cause the cantilever arms 56 a, 56 b todeflect. In one example, the reference surfaces 102 a, 102 b can beraised (e.g., stepped-up, upwardly offset, elevated, etc.) relative totops sides of the cantilever arms 56 a, 56 b.

It will be appreciated that the fiber alignment housing 40 defines aninternal chamber 99 or cavity for receiving the fiber alignmentsubassembly 42. Additionally, the fiber alignment housing 40 includesinternal features adapted to engage the fiber alignment subassembly 42to effectively position or center the fiber alignment subassembly 42within the fiber alignment housing 40. Preferably, the fiber alignmentsubassembly 42 is centered within the fiber alignment housing 40 suchthat the fiber alignment groove 48 coaxially aligns with the fiberinsertion axis 72. In certain examples, the fiber alignment housing 40includes side rails 104 that engage opposite sides of the fiberengagement component 44 to laterally center the fiber alignmentsubassembly 42. In certain examples, the side rails 104 include a pairof opposing side rails 104 a defined by the first housing piece 64 a anda pair of opposing side rails 104 b defined by the second housing piece64 b.

The fiber alignment housing 40 can also include internal structure forvertically centering the fiber alignment subassembly 42 within the fiberalignment housing 40. The internal structure can include an uppersubassembly positioning surface arrangement 106 and a lower subassemblypositioning surface arrangement 108 between which the fiber alignmentsubassembly 42 is vertically compressed. In certain examples, the uppersubassembly positioning surface arrangement 106 can engage the top side52 of the main body 50 of the fiber engagement component 44 and thelower subassembly positioning surface arrangement 108 can engage thebottom sides of the rods 62 a, 62 b. In this way, the rods 62 a, 62 bcan be compressed by the lower subassembly positioning surfacearrangement 108 into the elongate pocket 60. In certain examples, thelower subassembly positioning surface arrangement 108 includes surfaces108 a, 108 b positioned adjacent opposite ends of the rods 62 a, 62 b.In certain examples, surfaces 108 a can be defined by the first housingpiece 64 a and surfaces 108 b can be defined by the second housing piece64 b. The rods 62 a, 62 b can extend through a majority of the axiallength of the fiber alignment housing 40. In certain examples, the lowersubassembly positioning surfaces 108 a, 108 b can generally align withand oppose the reference surfaces 102 a, 102 b. In certain examples, thelower subassembly positioning surfaces 108 a, 108 b can be positionedadjacent to the fiber insertion openings 70 a, 70 b, respectively. Incertain examples, the upper subassembly positioning surface arrangement106 can include surfaces 106 a, 106 b defined by corresponding rails 107a, 107 b.

In certain examples, the lower subassembly positioning surfaces 108 a,108 b can be defined by corresponding tee-beams 110 a, 110 b. Thetee-beam 110 a corresponds to the first housing piece 64 a and thetee-beam 110 b corresponds to the second housing piece 64 b. Thetee-beams 110 have tee-shaped cross-sections defined by webs 112 andflanges 114. The flanges 114 are transversely oriented relative to thewebs 112 and include flange portions 116, 118 that project outwardlyfrom the webs 112. The flanges 114 include end faces 120 that oppose thebottom sides of the rods 62 a, 62 b. Portions of the end faces 120define the lower subassembly positioning surfaces 108 a, 108 b. Flangeportions 116 are adapted to engage the rod 62 a and flange portions 118are adapted to engage the rod 62 b. Space beneath the flange portions116, 118 allow the flange portions 116, 118 to flex slightly uponcontact with the rods 62 a, 62 b when the rods 62 a, 62 b are compressedagainst the reference surfaces 102 a, 102 b of the main body 50 of thefiber engagement component 44. The end faces 120 also include anglednon-contact sections 122 that angle away from the rods 62 a, 62 b as theangled portions extend away from their corresponding fiber insertionopenings 70 a, 70 b and toward the central interface plane 66. Thus,contact between the positioning surfaces 108 a, 108 b of the alignmenthousing 40 and the bottom sides of the rods 62 a, 62 b is eliminated atthe middle portion (e.g., at the central interface plane 66) of thealignment housing 40. This can prevent bulging at the middle portion.Additionally, within the pocket of the main body 50 at the middleportion, the side walls of the pocket are notched (e.g., recessed) atrecessed regions 53 to prevent lateral contact between the rods 62 a, 62b and the main body 50 to inhibit bulging of the main body at the middleportion.

When the fiber alignment device 20 is assembled, the fiber engagementcomponent 44 is compressed between the upper subassembly positioningsurfaces 106 a, 106 b and the first and second rods 62 a, 62 b. Also,the first and second rods 62 a, 62 b are compressed between the lowersubassembly positioning surfaces 108 a, 108 b and the reference surfaces102 a, 102 b of the fiber engagement component 44. The fiber engagementcomponent 44 and the first and second rods 62 a, 62 b are compressedtogether between the upper and lower subassembly positioning surfaces106, 108.

In certain examples, the main body 50 includes fiber insertion lead-instructures 51, 59 at opposite ends of the main body 50. The lead-instructures 51, 59 can extend through the reference surfaces 102 a, 102 b(e.g., see FIG. 10). The lead-in structures 51, 59 can be axiallyaligned with the fiber insertion axis 72, the fiber alignment groove 48,the transition portions 80 a, 80 b of the alignment housing 40 and thetab portions 96 a, 96 b of the cantilever arms 56 a, 56 b. Each of thelead-in structures 51, 59 includes a tapered section 55 (e.g., a partialfunnel, partial cone, etc.) that leads into a non-tapered groove section57.

FIGS. 11-13 show an example fiber alignment device 300 in accordancewith a fiber ribbon alignment construction or system to align fibersfrom ferrule-less connector plugs or other structures. In one example, afiber optic ribbon cable may include a plurality of optical fibers 308.Each of the plurality of optical fibers 308 includes a fiber axis 330and each of the plurality of optical fibers 308 includes a bare opticalfiber and a coating surrounding the bare optical fiber to form anexternal surface of the optical fiber.

The fiber alignment device 300 can be made from molded materials. Thefiber alignment device 300 includes a body 310 having a first end 312, asecond end 314, a top 316 (FIG. 12) and a bottom 311 (FIG. 13). Thefirst end 312 defines a first opening 303 and the second end 314 definesan opposite second opening 304. The first and second openings 303, 304each provide for optical fibers 308 to be centered and oriented in thebottom 311 of the fiber alignment device 300. The bottom 311 has aplurality of groove structures 306 integrally formed, such as aV-grooves, or gaps, or slots. It will be appreciated that the groovestructures 306 can include other groove profiles using various materialsand manufacturing processes.

Each of the plurality of optical fibers 308 may be inserted through thebottom 311 of the first and second openings 303, 304 such that thefibers are disposed within the groove structures 306 in a substantiallyuniform orientation to facilitate centering and alignment of a firstplurality of optical fiber 308 a with a second plurality of opticalfiber 308 b. In this manner, as a non-limiting example, the fiberalignment device 300 provides an alignment of the first plurality ofoptical fibers 308 a in the first opening 303 to the second plurality ofoptical fibers 308 b in the second opening 304.

The top 316 of the body 310 of the fiber alignment device 300 comprisesa planar region 318. The planar region 318 contains a recess 320including a plurality of cantilever members 322. The cantilever members322 are arranged and configured on opposite sides of a fiber alignmentregion 305. The fiber alignment region 305 can help to facilitatecentering and alignment of the optical fibers 308 with another opticalfiber 308.

In one example, the plurality of cantilever members 322 extend from theplanar region 318 and project at least partially downward at an angletoward the optical fibers 308. It will be appreciated that the pluralityof cantilever members 322 may be configured to press the optical fibersin the grooves without being angled down. For example, a cantilevermember may include a bump (e.g., projection) that extends from the bodyof the cantilever to engage the fibers and press the fibers into arespective groove.

In one example, a first set of cantilever members 322 a are flexible andconfigured for urging each of the first plurality of optical fibers 308a into their respective groove structures 306 and a second set ofcantilever members 322 b are flexible and configured for urging each ofthe second plurality of optical fibers 308 b into their respectivegroove structures 306. In other words, the first and second sets ofcantilever members 322 a, 322 b respectively align the first and secondplurality of optical fibers 308 a, 308 b to one another.

As described above, a gel can be disposed within any fiber alignmentdevices disclosed herein.

Refractive-index matching, self-curing and self-cleaning gelcompositions and articles containing said compositions are provided thatare particularly suited for environmentally protecting substrates,especially optical fiber interfaces, which accomplish the previouslyrecited objects and retain the desired features recited previously whileproviding additional benefits readily apparent to the skilled artisanfrom the following more detailed description.

It is one objective that the gel compositions exhibit superior anduseful combinations of tensile strength, elongation, toughness, indexmatching, accepting high levels of diluent without significantsyneresis, particularly while under compression while maintainingbeneficial tack properties essential for self-curing and self-cleaninggel compositions.

In another objective, index-matching, self-healing and self-cleaning gelcompositions are provided for reduce signal loss or reflection withinthe optical fiber networks and protect the optical interface from theenvironment, sealing and encapsulating optical fiber interfaces andarticles used to protect said optical fiber interfaces are thereforesubjected to temperatures in the range from about −40° to about 60° oreven 70° C., to insect damage, to water (both liquid and vapor) and musthave means to enable the technician to reenter the box and alter orrepair contacts, connections, splices and optical fibers containedtherein.

In a further objective, index-matching, self-healing, self-cleaning gelsare provided for use in sealing connectors and adapters used in joiningoptical fibers. More specifically, in one aspect this invention providesa cured organopolysiloxane gel which contains crosslinks and unreactedcrosslinkable sites, the density of the crosslinks being C (crosslinksper gram) and the density of the unreacted crosslinkable sites being V(sites per gram) and V being less than about twelve fifths preferablyless than about nine fifths of C.

The term crosslink in this specification connotes a covalent bond formedby chemical reaction between two crosslinkable sites from which sitesdepend a total of three or more molecular segments; or at least twocovalent bonds, each formed by chemical reaction between twocrosslinkable sites, attaching a chemical moiety to at least two polymerchains such that the chemical moiety has at least three molecularsegments depending therefrom. Typically the chemical moiety is theresidue of a low molecular weight compound or a low molecular weightoligomeric material containing at least three crosslinkable sites.Specifically, the term crosslink contemplates both trifunctional(T-links) (that is crosslinks having three molecular segments dependingtherefrom) tetrafunctional (H-links) (that is crosslinks having fourmolecular segments depending therefrom) and higher functionalitycrosslinks.

In one embodiment, a method is provided for preparing a crosslinkedorganopolysiloxane gel which comprises reacting together: 1) aorganopolysiloxane containing first reactive groups; and 2) at least onecompound containing second reactive groups; said second reactive groupsin the compound being capable of reacting with said first reactivegroups in the organopolysiloxane; in the presence of a diluent, which isinert to said first and said second reactive groups, in an amount offrom at least about 40% by weight to about 95% by weight of the combinedweights of said diluent, said organopolysiloxane and said compound. Insome embodiments, the inert diluent is a cyclopolysiloxane having arefractive index higher than the organopolysiloxane.

Preferably in this and the following aspect the organopolysiloxanecontains an average of at least Y first reactive groups per moleculewhere Y is at least 2, the at least one compound contains an average ofat least W second reactive groups where W is at least 2, and the sum ofY and W is at least about 5.

In another aspect, this disclosure provides a kit comprising a first anda second container, each of said containers comprising at least onematerial selected from: (1) an organopolysiloxane containing firstreactive groups) and 2) a compound containing second reactive groups;and said second reactive groups in the compound being capable ofreacting with said first reactive groups in the organopolysiloxane; and3) a diluent, which is inert to reaction with said first and said secondreactive groups, in an amount of from at least about 40% by weight toabout 95% by weight of the combined weights of said diluent, saidorganopolysiloxane and said compound; the division of materials betweensaid first and said second container, which are separate, being suchthat said organopolysiloxane and said compound are stable when saidfirst and said second container are maintained at room temperature understorage conditions for 6 months. In some embodiments, the inert diluentis a cyclopolysiloxane having a refractive index higher than theorganopolysiloxane.

In a further aspect, the present disclosure provides organopolysiloxanegel compositions selected from the group consisting of: a compositionhaving hardness values as measured by a texture analyzer of from 1 to 50g with an ultimate elongation of at least about 500% for example atleast about 700%, yet more preferably at least about 1000%, for exampleat least about 1100%, a composition having hardness as measured by atexture analyzer of from 5 to 40 g with an ultimate elongation of atleast about 600% for example at least about 650%, yet more preferably atleast about 750%, for example at least about 900%, most preferably atleast about 1000%, a composition having hardness values as measured by atexture analyzer of from 10 to 20 g with an ultimate elongation of atleast about 400% for example at least about 450%, yet more preferably atleast about 500%, for example at least about 550%, most preferably atleast about 600%, a composition having hardness as measured by a textureanalyzer of from 1 to 15 g with an ultimate elongation of at least about250% for example at least about 275%, yet more preferably at least about325%, for example at least about 375%, most preferably at least about425%, or mixtures thereof.

As used herein, “gel” refers to the category of materials which aresolids extended by a fluid extender. The gel may be a substantiallydilute system that exhibits no steady state flow. As discussed in Ferry,“Viscoelastic Properties of Polymers,” third ed. P. 529 (J. Wiley &Sons, New York 1980), a polymer gel may be a cross-linked solutionwhether linked by chemical bonds or crystallites or some other kind ofjunction. The absence of the steady state flow may be considered to bethe definition of the solid-like properties while the substantialdilution may be necessary to give the relatively low modulus of gels.The solid nature may be achieved by a continuous network structureformed in the material generally through crosslinking the polymer chainsthrough some kind of junction or the creation of domains of associatedsubstituents of various branch chains of the polymer. The crosslinkingcan be either physical or chemical as long as the crosslink sites may besustained at the use conditions of the gel.

The index-matching gel may be substantially volumetricallyincompressible. By being substantially volumetrically incompressible,the index-matching gel exhibits hydraulic characteristics similar to orthe same as a liquid when placed under pressure

The index-matching gel composition may include a crosslinked gel anddiluent that exhibits good index match to the glass fiber, high opticalclarity, and low absorption loss.

Gels for use in this disclosure may be silicone (organopolysiloxane)gels, such as the fluid-extended systems taught at U.S. Pat. No.4,634,207 to Debbaut (hereinafter “Debbaut '207”); U.S. Pat. No.4,680,233 to Camin et al.; U.S. Pat. No. 4,777,063 to Dubrow et al.; andU.S. Pat. No. 5,079,300 to Dubrow et al., the disclosures of each ofwhich are hereby incorporated herein by reference in their entirety.These fluid-extended silicone gels may be created with nonreactive fluidextenders as in the previously recited patents or with an excess of areactive liquid, e.g., a vinyl-rich silicone fluid, such that it actslike an extender, as exemplified by the Sylgarde 200 productcommercially available from Dow-Corning of Midland, Mich. or asdisclosed at U.S. Pat. No. 3,020,260 to Nelson. Because curing isgenerally involved in the preparation of these gels, they are sometimesreferred to as thermosetting gels. The gel may be a silicone gelproduced from a mixture of divinyl terminated polydimethylsiloxane,tetrakis (dimethylsiloxy)silane, a platinum divinyltetramethyldisiloxanecomplex, commercially available from United Chemical Technologies, Inc.of Bristol, Pa., polydimethylsiloxane, and/or1,3,5,7-tetravinyltetra-methylcyclotetrasiloxane (reaction inhibitor forproviding adequate pot life).

Examples of vinyl terminated polysiloxanes appear in U.S. Pat. No.4,196,273 to Imai et al. Vinyl terminated polysiloxanes may becrosslinked with themselves or with other polysiloxanes containingvarious functional groups such as aryl, aliphatic (saturated orunsaturated), and fluoroaliphatic moieties (such as CF3 CH2-) orcontaining other groups such as nitrogen groups, sulphur groups and thelike. Examples of such organopolysiloxanes are shown in U.S. Pat. No.3,624,022 to Ross, U.S. Pat. No. 4,064,027 to Gant, U.S. Pat. No.4,163,081 to Schulz and U.S. Pat. No. 3,445,420 to Kookootuedes.Diorganopolysiloxanes terminated at the chain ends with two or threevinyl groups have been crosslinked to provide elastomeric or rubber-typeproducts, as shown in U.S. Pat. No. 4,364,809 to Sato et al.

An additional aspect of this invention provides articles for protectingsubstrates, said articles comprising cured organopolysiloxane gel whichcontains crosslinks and unreacted crosslinkable sites, the density ofthe crosslinks being C (crosslinks per gram) and the density ofunreacted crosslinkable sites being V (sites per gram) wherein V is lessthan about twelve fifths preferably less than nine fifths of C(crosslinks per gram).

Still another aspect of this invention comprises a substrateprotectively encapsulated at least in part by a cured organopolysiloxanegel which contains crosslinks and unreacted crosslinkable sites, thedensity of the crosslinks being C (crosslinks per gram) and the densityof unreacted crosslinkable sites being V (sites per gram) wherein V isless than about twelve fifths, preferably less than about nine fifths ofC (crosslinks per gram). A still further aspect of this inventionprovides a method for protecting a substrate comprising: (1) providing acured organopolysiloxane gel which contains crosslinks and unreactedcrosslinkable sites, the density of the crosslinks being C (crosslinksper gram) and the density of unreacted crosslinkable sites being V(sites per gram) wherein V is less than about twelve fifths, preferablyless than about nine fifths of C (crosslinks per gram), (2) applyingsaid cured organopolysiloxane gel to said substrate such that saidcomposition substantially encapsulates at least a portion of saidsubstrate.

A further additional aspect of this invention provides a method forprotecting a substrate comprising: (1) providing a first meanscomprising a cured organopolysiloxane gel which contains crosslinks andunreacted crosslinkable sites, the density of the crosslinks being C(crosslinks per gram) and the density of unreacted crosslinkable sitesbeing V (sites per gram) wherein V is less than about twelve fifthspreferably less than about nine fifths of C (crosslinks per gram), (2)applying a force means for acting on said first means so that said curedorganopolysiloxane gel is maintained in compressive contact with saidsubstrate and substantially encapsulates at least a portion of saidsubstrate.

Thus it is highly desirable that cured gels useful in these and similarapplications possess excellent physical properties, including matchingrefractive index to about that of an optical fiber, high elasticity,self-cleaning, self-curing, and elongation to provide highdeformability; high toughness (a combination of high elongation andtensile strength), a cohesive strength greater than its adhesivestrength and greater adhesion to the apparatus containing it than to thesubstrate to ensure the gel remains substantially within the apparatuswhen it is removed; excellent tack, adhesive properties, resistance tostress relaxation and low compression set to prevent water ingress alongthe interface between the gel and the bare optical fibers or connector;good stability to syneresis under compression (as hereinbelow described)to prevent shrinkage of the gel and contamination of its environment;high hydrolytic, thermal stability; that it be moisture insensitive andthat it possess excellent resistance to the damaging effects ofultra-violet (u. v.) light to enable it to survive exposure to theelements for the long service life contemplated for such devices.

The index-matching gel may be prepared from a base gel compositioncomprising one or more polysiloxanes, also known as silicones. Thepolysiloxane or silicone fluids may be reactive silicone polymersformulated with dialkyl and/or diaryl silicone polymers. In someembodiments, the silicone polymers include dimethyl, methylphenyl,diphenyl, and/or trifluoropropylmethyl constituent groups, withrefractive index ranging from about 1.38 to about 1.60, about 1.38 toabout 1.57, or about 1.39 to about 1.42 when measured at a wavelengthselected from 402 nm, 589.3 nm, 633 nm, 980 nm, or 1550 nm according toASTM D-1218.

Silicone curing gels may contain reactive silicone polymers and reactivesilicone crosslinkers in a two-part system. When mixed together thesematerials are designed to have a very soft and compliant feel when curedand will stick to substrates without migrating. Viscosities can beadjusted with the molecular weight of the polymers from 200-10,000 cP.Depending on the functionality of the polymer, optical index matchingcan be formulated in the range of 1.38-1.57 by ASTM D-1218. Thesetwo-part systems contain reactive polymers and crosslinkers that cure upto a rubbery type hardness. Most will cure at room temperature, howeversome need heat to cure. To impart increased physical properties,typically these materials have higher viscosities. These materials'viscosity may depends largely on molecular weight of the polymer andsteric hindrance of functional groups on the polymer chain and can rangefrom 100 cP (a light oil) to an extremely thick gum polymer.

In some embodiments, the combined weights of organopolysiloxane andcompound used to prepare cured organopolysiloxane gel is from about 5 toabout 60% of the combined weights of diluent, organopolysiloxane andcompound.

In some embodiments, the average molecular weight between crosslinks(Mc) of the cured organopolysiloxane gel is at least about 15,000, morepreferably at least about 20,000, for example at least about 40,000, yetmore preferably at least about 60,000, for example at least about100,000, most preferable at least about 150,000 for example at leastabout 200,000.

In some embodiments, the organopolysiloxane has been cured in thepresence of a diluent inert under the conditions used to cure theorganopolysiloxane in an amount of from about 40 to about 95% by weightof the combined weights of said organopolysiloxane and said diluent.

In some embodiments, the organopolysiloxane has been cured from a 2 partcomposition, wherein the combined part 1 and part 2 may contain

1) diluent comprising a nonreactive cyclosiloxane, such as a diphenyl ortetraphenyl cyclosiloxane and/or a trimethyl terminatedpolydimethylsiloxane, and optionally a monofunctional diluent such as amonovinyl terminated polydimethylsiloxane,

2) organopolysiloxane, such as a vinyldimethyl terminatedpolydimethylsiloxane;

3) a compound having at least 3 or at least 4 functional Si—H groupssuch as phenyl Tris(dimethylsiloxy)silane orTetrakis(dimethylsiloxy)silane;

4) a platinum catalyst; and/or

5) optionally a cure inhibitor.

In some embodiments, the organopolysiloxane has been cured from a 2 partcomposition, wherein the combined part 1 and part 2 may contain

1) an organopolysiloxane, such as a vinyl-terminatedpolydimethylsiloxane;

2) a compound having at least 3 or at least 4 functional Si—H groupssuch as phenyl Tris(dimethylsiloxy)silane orTetrakis(dimethylsiloxy)silane;

3) a platinum catalyst; and

4) optionally a cure inhibitor.

In some embodiments, the gel composition has a hardness as measured by atexture analyzer of about 1 to 50 g with an ultimate elongation of atleast about 250%, more preferably a hardness as measured by a textureanalyzer of about 2 to about 40 g, most preferably about 5 to about 30g, and more preferably has an ultimate elongation of at least about650%, for example, at least about 700%, yet more preferably at leastabout 800%.

In some embodiments, cured gel compositions are provided that aremoisture insensitive. Preferably also the cured organopolysiloxane gelcompositions of the invention contain minimum amounts of ionic speciesas particulate sodium borate, for example less than about 1800 ppm ofthe weight of the composition as particulate sodium borate, morepreferably less than about 1500 ppm of the weight of the composition asparticulate sodium borate. Most preferably the compositions aresubstantially free of particulate sodium borate.

The term substantially free of particulate sodium borate when applied tocurable compositions and curing or cured organopolysiloxane gels of theinvention connotes that the said compositions or gels are free of addedparticulate sodium borate as a discrete chemical entity. This term isnot intended to exclude materials, such as sodium borate containingessentially water insoluble glasses, which contain the elements ofsodium borate, but not in a discrete chemical form.

In one embodiment, a crosslinked organopolysiloxane is provided whichhas been crosslinked in the presence of from about 40 to about 95% byweight of a diluent (based on the combined weights of said crosslinkedorganopolysiloxane plus said diluent), said diluent being inert underthe conditions used to crosslink the organopolysiloxane

In another embodiment, a cured organopolysiloxane gel is providedcomprising from about 40% up to about 95% by weight of a diluent (basedon the combined weights of the organopolysiloxane and the diluent),which diluent is inert under the curing conditions used to crosslinksaid organopolysiloxane and said organopolysiloxane having beencrosslinked in the presence of said diluent.

The term unreacted crosslinkable sites connotes reactive sites initiallypresent in the reaction mixture used to prepare cured organopolysiloxanegel which by virtue of stoichiometric imbalance or other reason survivethe curing process without producing crosslinks or causing chainextension. As pointed out above, the average density of unreactedcrosslinkable sites in the cured organopolysiloxane gel is less thanabout twelve fifths preferably nine fifths of C.

In some embodiments, if the crosslinks have an average functionality ofF where F is at least 3, the ratio of the average molecular weightbetween cross-links to (F-1) is at least about 7,000. Preferably also,the ratio of the average distance between crosslinks to (F-1) when theorganosiloxane chains are fully extended is at least about 250 Angstromunits.

In some embodiments, each molecular segment of organopolysiloxanebetween reacted first reactive groups is at least 250 Angstrom unitslong when the molecular chains are fully extended. Generally the densityof reactive crosslinkable sites in the cured composition is less thanabout twelve fifths of C, preferably less than about nine fifths of C;and in some embodiments the density of reactive crosslinkable sites ismore preferably less than about three halves of C, for example, lessthan about six fifths of C, most preferably less than about four fifthsof C, for example less than about three fifths of C. We have found thateven when 1:1 stoichiometric ratios of compound to organopolysiloxaneare used, frequently not all the reactive sites react to formcrosslinks. Although we do not want to be limited to any particularexplanation, this may occur because some of the reactive sites becomeentrapped in the crosslinked gel or are by other means prevented fromreaction.

In some embodiments, the average molecular weight between crosslinks(that is, the average molecular weight of all molecular segments whichare part of the closed loop three dimensional network) in the curedorganopolysiloxane gel is at least about 1300/(1-s)² where s is thediluent fraction of the cured organopolysiloxane gel. More preferably, Min the cured organopolysiloxane gel is at least about 1900/(1-s)², mostpreferably at least about 2600/(1-s)².

In some embodiments, the molar equivalent ratio of the compound orcombination of compounds to the organopolysiloxane is such that amajority of the molecules of reactants are joined to one or more othermolecules by at least two crosslinks (that is form closed loops whichcomprise at least part of a three dimensional network). More preferablyin these embodiments at least about 50%, for example at least about 65%,preferably at least about 75% of the crosslinks form such closed loops.

In some embodiments, the crosslinkable site is a reactive site capableof reacting with another reactive site to produce either chain extensionor crosslinking. By chain extension is meant the reaction of anorganopolysiloxane having at least 2 first reactive groups with acompound having 2 second reactive groups such that the molecular weightof the organopolysiloxane is increased without necessary formation ofcrosslinks. The term cured organopolysiloxane gel′ connotes that theorganopoly-siloxane has been maintained under curing conditions at acuring temperature for a sufficient time that the hardness as measuredby a texture analyzer of said gel is not significantly increased if thecuring time is doubled.

In some embodiments, a method is provided comprising reacting one ormore compounds having at least three second reactive groups and at leastone compound having two second reactive groups with the first reactivegroups of the organopolysiloxane and of forming covalent bonds thereto.In this embodiment of the invention it is not preferred that theselected organopolysiloxane have a ratio of the weight average molecularweight to Y of at least 7000. It is preferred that the relative amountsof the compound having only 2 reactive groups per molecule and theorganopolysiloxane be such that if said compound is reacted with saidorganopolysiloxane alone, the resultant organopolysiloxane would have aratio of the weight average molecular weight to the average number offirst reactive groups per molecule of at least 7000.

In certain embodiments, each reactive site in said organopolysiloxaneand said compound is independently selected from the group consisting ofvinyl, hydroxy, acyloxy, amine, oxime and alkoxy groups and hydrogen andhalogen, for example chlorine, directly bonded to silicon, with theproviso that the ratio of silicon bonded hydrogens to unsaturatedaliphatic groups, if both are present in the composition, is from about0.67 to about 1.5.

In some embodiments, the organopolysiloxane has a weight averagemolecular weight of at least 14,000 and is selected from one or more of

where each n is independently at least about 4, m is at least 1, t isfrom at least 2 to 4 and each main chain unit D is independentlyselected from the group consisting of:

where each R is independently selected from divalent unsubstituted andsubstituted alkyl and aryl moieties and each R1 is independentlyselected from substituted and unsubstituted monovalent hydrocarbongroups free of aliphatic unsaturation; and, each A is independentlyselected from the group consisting of a valence bond and main chain

units of the structure:where k is from 1 to 10, preferably from 1 to 5; and each Q and Q′ isindependently:

where i is from 1 to 10, preferably from 1 to 5; and X is an aliphaticaromatic or organosilyl moiety as defined hereinbelow valence bonded totxA moieties.

In some embodiments, the second component comprises at least onecompound capable of reacting with and curing the first component andselected from the group consisting of: 1) polyunsaturated organicaliphatic, aromatic and alkyl aromatic compounds; and 2) linear,branched and cyclic organosiloxanes selected from the group having thegeneral formulae;

where each n is independently at least about 4, m is at least 1, t isfrom at least 2 to 4 and each main chain unit D is independentlyselected from the group consisting of:

where each R is independently selected from divalent unsubstituted andsubstituted alkyl and aryl moieties and each R1 is independentlyselected from substituted and unsubstituted monovalent hydrocarbongroups free of aliphatic unsaturation; and, each A is independentlyselected from the group consisting of a valence bond and main chainunits of the structure:

where k is from 1 to 10, preferably from 1 to 5; and each Q and Q′ isindependently:

where i is from 1 to 10, preferably from 1 to 5; and X is an aliphaticaromatic or organosilyl moiety as defined hereinbelow valence bonded tot×A moieties. linear, branched and cyclic organosiloxanes having thegeneral formula

where p has a value of from 1 to 4 and J is:

where v has a value of at least 0; and E is selected from the groupconsisting of a valence bond and R2 groups; and G is selected from avalence bond and the group consisting of substituted and unsubstitutedmonovalent and polyvalent silicon atoms and carbon atoms directly linkedby valence bonds to p J groups and to (4−p) R₂ groups.

Each R₂ if present in the elements A, Q, Q′, J and E of the abovepreferred embodiments of the organopolysiloxane and compound isindependently selected from the group consisting of substituted andunsubstituted monovalent hydrocarbon groups free of aliphaticunsaturation and reactive groups.

Preferably any Q or Q′ group in component A not containing any reactivesubstituent is less than about 20, preferably less than about 10 mainchains units from the nearest main chain unit containing at least onereactive group in the same molecule.

X in the reactive organopolysiloxane is preferably selected fromdivalent moieties such as —S—, —O—, —NR— and

where each R is independently selected from divalent unsubstituted andsubstituted alkyl and aryl moieties and each R5 is independently definedas above; and trivalent moieties such as —N—, —P— and —P(O)— andtrivalent substituted and unsubstituted hydrocarbon groups free ofaliphatic unsaturation,

where R2 is as defined above.

In some embodiments, the number of reactive groups in each molecule ofthe organopolysiloxane is at least 2 and the ratio of the average totalnumber of main chain units in the reactive organopolysiloxane of thefirst component to the average number of reactive groups containedtherein is at least about 50, preferably at least about 100, for example150.

The term substituted and unsubstituted monovalent hydrocarbon groupsfree of aliphatic unsaturation connotes alkyl, aryl, alkyl-aryl, halogensubstituted groups such as chloro- or fluoro-alkyl or -aryl, cyanoalkyland cyanoaryl.

In some embodiments, the organopolysiloxane may be selected from one ormore of dimethylpolysiloxanes, diphenylpolysiloxanes,diphenyldimethylpolysiloxane copolymers, and cyclosiloxanes.

The term “PDMS” refers to polydimethylsiloxane.

The term “hydride terminated PDMS” refers to Si—H hydride terminatedpolydimethylsiloxane.

The term “vinyl-terminated PDMS” refers to vinyl-terminatedpolydimethylsiloxane. In some embodiments, the organopolysiloxane is areactive dimethylpolysiloxanes having a formulaCH₂═CH—Si(CH₃)₂—O—[—Si(CH₃)₂—O—]n-Si(CH₃)₂—CH═CH₂, having reactive vinylend groups, wherein n is sufficient to impart a molecular weight asdescribed herein. Dimethylpolysiloxanes typically exhibit a refractiveindex of about 1.40, 25° C. at 598 nm.

In some embodiments, the organopolysiloxane is a reactivediphenyldimethylpolysiloxane copolymer including a diphenylfunctionality, e.g.,CH₂═CH—Si(CH₃)₂—[—Si(CH₃)₂—O]n-[Si(Ph)₂-O]m-Si(CH₃)₂—CH═CH₂, wherein nand m are sufficient to impart a molecular weight as described hereinand m>1. which may increase the refractive somewhat compared todimethylpolysiloxanes. The refractive index may range from 1.40 to 1.60at 25° C. at 598 nm, depending on proportion of phenyl functionalities.

In some embodiments, the organopolysiloxane is a fluorosilicone based ontrifluoropropyl methyl polysiloxane polymers, e.g.,CH₂═CH—Si(CH₃)₂—O—[—Si(CH₃)(CH₂CH₂CF₃)—O—]n-Si(CH₃)₂—CH═CH₂, which mayexhibit a typical refractive index of 1.38 at 25° C. at 598 nm. Thetrifluoropropyl group contributes polarity to the polymer to result inswell resistant to organic solvents such as gasoline or jet fuel. Theterm ‘capable of reacting with and curing said first component’ connotesthat the reactive sites in the first and second components are soselected that a major portion of the crosslinks formed areintermolecular (that is they are formed between differentorganopolysiloxane molecules) and only a minor portion of the crosslinksformed are intramolecular (that is, they are formed between reactivesites in the same organopolysiloxane molecule).

In some embodiments, a cured organopolysiloxane gel is provided having ahardness as measured by a texture analyzer (B) of from about 1 to about50 g and an ultimate elongation (U) of at least about 100%, such that:where K is at least about 1700, for example at least about 1800,preferably at least about 2000, for example at least about 2200, mostpreferably at least about 3000, for example at least about 3500.Preferably in this embodiment the hardness as measured by a textureanalyzer is from 2 to 40 g and preferably the ultimate elongation is atleast about 150, for example at least about 250 more preferably at leastabout 300%.

In some embodiments, a cured organopolysiloxane gel composition isprovided having a hardness as measured by a texture analyzer of fromabout 1 to about 50 g with an ultimate elongation (U) of at least 100%such that: where Ts is the tensile strength of the composition and L isat least about 45, for example at least about 50, preferably at leastabout 60, for example at least about 70, most preferably at least about80, for example at least about 90. Preferably in this embodiment alsothe hardness as measured by a texture analyzer is from 5 to 40 g and theultimate elongation preferably at least about 150%, for example at leastabout 250%, more preferably at least about 300%.

In some embodiments, a crosslinked gel composition is provided having ahardness as measured by a texture analyzer, or Voland hardness, of fromabout 1 to about 40 g, preferably about 5 to about 30 g, most preferablyabout 10 to about 20 g and an ultimate elongation of at least about500%, more preferably at least about 1000%, most preferably at leastabout 1100%.

In some embodiments, articles and methods are provided for protecting asubstrate, which may comprise an optical fiber interface, which employthe cured organopolysiloxane gels as described in any one or more of theabove aspects and embodiments of the present invention, and assembliescomprising a substrate at least partially encapsulated by the gelcompositions as described in one or more of the above aspects andembodiments of the present invention; particularly those gels and gelcompositions having the above enumerated combinations of hardness asmeasured by a texture analyzer and ultimate elongation properties and/ortensile strength and ultimate elongation properties.

In some embodiments, articles are provided comprising a cured gel forprotecting a substrate wherein the organopolysiloxane may be pre-cured(that is, cured before coming into contact with the substrate), or curedafter coming into contact with the substrate. In one aspect, theorganopolysiloxane gel is cured before contacting the optical fibersubstrate. If the organopolysiloxane is pre-cured, the articles andmethods include means for deforming the cured organopolysiloxane gelinto contact, which preferably is close and conforming contact, with anoptical fiber substrate. Such means for deforming the gel into contactwith the substrate may comprise a force means or a means for compressingthe gel into contact with the substrate and/or means for maintaining thecured organopolysiloxane gel in contact with the substrate bycompression.

In some embodiments, cured organopolysiloxane gels and gel compositionsare provided having a cohesive strength greater than the adhesivestrength of the said gel or composition.

The term valence bond connotes a single covalent bond directly linkingtwo atoms of the main chain of organopolysiloxane or compound ororganopolysiloxane and compound together.

The term cured organopolysiloxane gel connotes that portion of thecompositions of the invention containing siloxane or organic moieties.Thus the cured organopolysiloxane gel contains the unreactive diluentand wholly or partly reacted products derived from reaction of first andsecond components as described hereinabove.

The index-matching gel composition may include one or more unreactivediluents, or chain extenders, as provided in U.S. Pat. No. 5,079,300,incorporated herein by reference in its entirety.

The diluent may be chosen from a variety of inert diluents which arecompatible with organopolysiloxanes and gels thereof. Preferably thediluent is an organosiloxane inert under the crosslinking conditionsused to prepare the cured organopolysiloxane gel and having a viscosityof from about 1 to about 10⁶ centipoises (cp), preferably from about 30to about 1000000, for example about 50 to about 30000.

The molecular weight of the diluent in general may be from about 100 toabout 200,000 Daltons preferably about 1,000 to about 140,000, mostpreferably about 4,000 to about 50,000 although the preferred and highlypreferred ranges generally will depend on the diluent concentration andthe average molecular weight between crosslinks as disclosed in theexamples.

In some embodiments the diluent comprises a dimethylsiloxane although insome circumstances it may be desirable to provide a methyl phenylsiloxane or mixtures and copolymeric oligomers of dimethylsiloxanes anddiphenyl siloxanes, depending on the desired degree of compatibilitywith the crosslinked polysiloxane. Without being bound by theory, themolecular weight of the inert diluent may play a role in determining theproperties of the cured organopolysiloxane gel.

The index-matching gel may include one or more unreactive diluents inertunder the curing conditions used to crosslink said organopolysiloxaneand said organopolysiloxane having been crosslinked in the presence ofsaid diluent.

In specific embodiments, the inert diluent includes one or more diluentnon-reactive cyclosiloxanes. The cyclosiloxane may be selected from acyclotrisiloxane (D3), cyclotetrasiloxane (D4), cyclopentasiloxane (D5),cyclohexasiloxane (D6), cycloheptasiloxane (D7). The cyclosiloxane basemay be characterized by the number of “D” units ((CH₃)₂SiO) in thecyclic structure, with D3 indicating cyclotrisiloxane base(hexamethylcyclosiloxane), and so forth. Each D unit on the base has 2methyl(CH₃) functional groups. Within a cyclosiloxane base, one, two,three, four, or more of the methyl groups may be replaced by phenylgroups. In some embodiments, phenyl groups replace both methyl groups onthe same D unit, resulting in a diphenyl cyclosiloxane base, or four ofthe methyl groups can be replaced by phenyl groups resulting in atetraphenyl cyclosiloxane base; or six of the methyl groups can bereplaced by phenyl groups resulting in a hexaphenyl cyclosiloxane. Thecured index-matching gel may include about 40% up to about 95% byweight, or about 45% up to about 85% by weight, or about 50% to about80% by weight of an unreactive diluent.

In some embodiments, the refractive index of the non-reactive diluent ishigher than that of the curable or cured crosslinked gel withoutdiluent. In this way, the gel may be tuned to a particular refractiveindex by addition of the non-reactive diluent. In particular, theindex-matching base gel composition may include one or more of a diluentdiphenyl cyclotrisiloxane(D3); triphenyl cyclotrisiloxane (D3), diphenylcyclotetrasiloxane (D4), tetraphenyl cyclotetrasiloxane (D4), hexaphenylcyclotetrasiloxane (D4); methyl cyclopentasiloxane (D5), diphenylcyclopentasiloxane (D5), tetraphenyl cyclopentasiloxane (D5), hexaphenylcyclopentasiloxane (D5); methyl cyclohexasiloxane (D6), diphenylcyclohexasiloxane (D6), tetraphenyl cyclohexasiloxane (D6), hexaphenylcyclohexasiloxane (D6); diphenyl cycloheptasiloxane(D7), or a mixturethereof. In particular, the index-matching base gel composition mayinclude one or more of a diluent selected from1,1-diphenyltetramethylcyclotrisiloxane (CAS RN 1693-51-2),1,3,5-triphenyltrimethylcyclotrisiloxane (CAS RN 546-45-2),2,2,4,4,6,6-hexamethyl-8,8-diphenyl-cyclotetrasiloxane,octamethyldiphenyl-cyclopentasiloxane, decamethyl diphenylcyclohexasiloxane, tetramethyltetraphenyl-cyclotetrasiloxane, orhexamethyl tetraphenyl-cyclopentasiloxane. In some specific embodiments,the diluent is 2,2,4,4,6,6-hexamethyl-8,8-diphenyl-cyclotetrasiloxane,CAS RN: 1693-44-3, Refractive Index 1.513, MW. 428.82 g/mol,commercially available from Alfa Chemistry, US, ACM1693443, or ChemosGmbH, Germany, c23372270. In some embodiments, the diluent is1,1-diphenyltetramethylcyclotrisiloxane, CAS RN 1693-51-2, availablefrom ChemTik, Berlin, Germany, Product Code: CTK4D3277. In someembodiments, the diluent is 1,3,5-triphenyltrimethylcyclotrisiloxane,CAS RN 546-45-2, available from GELEST, Morrisville, Pa., Product Code:SIT8705.0.

In some embodiments, cured organopolysiloxane gels are provided usinglarger amounts of inert diluent to improve one or more properties suchas decreased time to self-cure, improving self-cleaning, or tailoringtack while decreasing tear-out after at least 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, or more cycles of removing the optical fiber from the gel.

In some embodiments, as the molecular weight of the diluent is increasedthe tack exhibited by a given cured organopolysiloxane gel increases. Insome embodiments, as the molecular weight of the diluentis increased,evidence of incompatibility, for example, syneresis is evidenced.

The term syneresis connotes the “bleeding” or exuding and exclusion froma cured organopolysiloxane gel of at least a portion of the diluent inwhich the cured organopolysiloxane gel was prepared or swollen. Thischaracteristic is particularly likely to be exhibited if a curedorganopolysiloxane gel containing diluent is subjected to compression.One way to measure stability to syneresis is by immersing cured gel intofresh diluent and measuring the amount of fluid uptake. Higher stabilityis indicated by larger diluent uptake. Stability may also be measured bycompressing a cured gel sample until a pressure level is reached atwhich syneresis commences. Higher compression forces indicate morestable gels. Another way to measure syneresis is by aging the gel undera specific condition, followed by loss in weight of the gel. In someembodiments, there are preferred ranges of diluent molecular weight forbest combinations of tack, stability to and absence of significantsyneresis under compression and the other hereinabove mentioned superiorphysical properties desired in cured organopolysiloxane gels especiallycured organopolysiloxane gel compositions.

In general the greater the distance between crosslinks in the curedorganopolysiloxane gel, the higher the upper limit of the preferredrange of diluent molecular weights. In some embodiments, the curedorganopolysiloxane gels having Mc values of at least about 15,000prepared in the presence of inert diluents of number average molecularweight (Mn) between about 100 and about 15,000 exhibit especiallybeneficial tack properties and stability towards syneresis as describedabove; the more preferred range of diluent Mn is about 1000 to about5,500; the most preferred range of diluent Mn is about 4,000 to 5,500.

Cured organopolysiloxane gels having Mc values of at least about 20,000and 40,000 prepared in the presence of inert diluents further comprisinga diluent having Mn from about 100 to 20,000 may exhibit especiallybeneficial tack properties and stability towards syneresis as describedabove; the more preferred range of diluent Mn is about 1000 to about10,000; the most preferred range of diluent Mn is about 4,000 to 10,000.Cured organopolysiloxane gels having Mc values of from about 40,000 toabout 60,000 may be prepared in the presence of inert diluent of Mn fromabout 100 to about 40,000 exhibit especially beneficial tack propertiesand stability towards syneresis as described above; the more preferredrange of diluent Mn is about 1000 to about 20,000; the most preferredrange of diluent Mn is about 4,000 to 20,000. Cured organopolysiloxanegels having Mc values from about 60,000 to about 100,000 prepared in thepresence of inert diluent of Mn from about 100 to about 60,000 exhibitespecially beneficial tack properties and stability towards syneresis asdescribed above; the more preferred range of diluent Mn is about 1000 toabout 35,000; the most preferred range of diluent Mn is about 4,000 to30,000. Organopolysiloxane gels having Mc values from about 100,000 toabout 200,000 prepared in the presence of inert diluent of Mn from about100 to about 100,000 may exhibit beneficial tack properties and may bestable to syneresis as described above; the range of additional diluentMn is about 1000 to about 55,000; or 4,000 to 30,000. Curedorganopolysiloxane gels having Mc values of at least about 200,000prepared in the presence of inert diluent of Mn from about 100 to about200,000 may exhibit especially beneficial tack properties and stabilitytowards syneresis as described above; the more preferred range ofdiluent Mn is about 1000 to about 100,000; the most preferred range ofdiluent Mn is about 4,000 to 30,000. It should be noted that withadditional dimethyl siloxane oligomeric diluents of molecular weightsignificantly above 25,000 particular care is necessary to ensureadequate dispersing and mixing of the reactive components used toprepare the cured organopolysiloxane gel.

In some embodiments, the diluent includes only a nonreactive diluent. Insome embodiments, the diluent may further include a mono functionalvinyl diluent.

In addition, the index-matching gel may be prepared from a compositionincluding chain extenders.

The index-matching gel may be prepared from a composition comprising apolymeric liquid selected from polyether polyols and end-substitutedpolyether polyols having a refractive index in the range 1.44-1.52.Examples of polymeric liquids are polymethylene glycol, polyethyleneglycol, polypropylene glycol, polyisopropylene glycol,poly(oxyethylene-oxypropylene)glycol, poly(oxymethylene)dimethyl ether,poly(oxypropylene)dipropyl ether, poly(oxyethylene)dipropyl amines,poly(oxypropylene)monoethyl ether, and the like.

Stability to syneresis may be measured by immersing cured gel into freshdiluent and measuring the amount of fluid uptake. Higher stability isindicated by larger diluent uptake. Stability may also be measured bycompressing a cured gel sample until a pressure level is reached atwhich syneresis commences. Higher compression forces indicate morestable gels. Of course, as is understood by those of ordinary skill inthe art, the ability to withstand compression without exhibitingsyneresis depends on a number of factors including but not limited todiluent compatibility with the crosslinked organopolysiloxane, diluentconcentration, the molecular weight between crosslinks of thecrosslinked organopolysiloxane and the temperature of the gel.

In some embodiments, index matching curable gels include a firstcomponent including a first component that is a reactiveorganopolysiloxane and a second component containing a reactivecrosslinker.

Reactive polysiloxanes useful for the first component of compositions ofthe invention include one or more of hydroxy-, alkoxy-, acyloxy-,amino-, oxime-, hydrogen- and vinyl-dimethyl and dihydroxy-, diacyloxy-,diamino-, dioxime-, dialkoxy-, dihydrogen- and divinyl-methyl terminatedpolydimethylsiloxanes and hydroxy-, alkoxy-, acyloxy-, amino-, oxime-,hydrogen- and vinyl-dimethyl and dihydroxy-, diacyloxy-, diamino-,dioxime-, dialkoxy-, dihydrogen- and divinyl-methyl terminateddimethylsiloxane copolymers with diphenyl siloxanes and non-siloxanemonomers such as alkylene oxides, for example ethylene and propyleneoxide and mixture thereof, divinyl benzene, styrene, andalpha-methylstyrene and tetramethyldisiloxane-ethylene, dimethylsiloxane-silphenylene and dimethyl siloxane-silphenylene oxidecopolymers, dimethyl siloxane-alpha-methylstyrene anddimethylsiloxane-bis-phenol A carbonate block copolymers. Thesepreferred siloxane polymers, copolymers and block copolymers may alsocontain the above indicated reactive functionalities dispersed along themain chain provided that the reactive functionalities are sufficientlyfar apart as indicated hereinabove.

In some embodiments, materials for use in the second componentcontaining reactive groups capable of reacting with and curing the firstcomponent include one or more of unsaturated aliphatic, aromatic oralkyl-aromatic compounds such as diallyl maleate, diallyl fumarate,triallyl citrate, divinyl adipate, divinyl benzene, diallyl phthalate,triallyl mellitate, tetraallyl pyromellitate, triallyl cyanurate,triallyl isocyanurate, glycerine triacrylate and trimethacrylate,pentaerythritol tri- and tetra-acrylate and -methacrylate which areexamples of low molecular weight compounds containing at least threecrosslinkable sites; the hereinabove mentioned preferred materials forthe first component, otherwise similar materials of lower molecularweight which are examples of oligomeric materials containing at leastthree crosslinkable sites; and siloxanes such astetrakis(dimethylsiloxy)silane, methyltris(dimethylsiloxy)silane,phenyl-tris(dimethylsiloxy)silane, tetraethoxysilane,tetramethoxysilane, phenyl triethoxysilane, methyl triethoxysilane,phenyl triacetoxysilane, 1,3,5,7-tetramethyltetravinylcyclotetrasiloxane and 1,3,5,7-tetra-methylcyclotetrasiloxane.

The index-matching gel may be prepared from a composition capable ofbeing further polymerized or crosslinked by means of heat or actinicradiation. Such compositions may contain monomers, oligomers, and highermolecular weight, liquid pre-polymers (including liquid siliconepre-polymers) having the required refractive index that have attachedthereto vinyl, acrylate, epoxy, isocyanate, silane, hydride,hydrosilane, and other polymerizable functional groups well known tothose skilled in the polymer art. Typically polymerizable compositionsalso contain initiators, catalysts, accelerators, sensitizers, and thelike to facilitate the polymerization process.

Especially when materials comprising first and second component containvinyl groups and silicon bonded hydrogen atoms, use of a catalyst ispreferred to facilitate reaction and cure.

Catalysts for such reactions are well known to those of ordinary shallin the art and include platinum compounds. Suitable platinum catalystsinclude platinum-divinyltetramethyldisiloxane complex in xylene (UnitedChemical Technologies (UCT), Bristol, Pa., PC072), or in vinylterminated polydimethylsiloxane (United Chemical Technologies (UCT),Bristol, Pa., PC075) or platinum-cyclovinylmethylsiloxane complex incyclic vinylmethylsiloxanes (United Chemical Technologies (UCT),Bristol, Pa., PC085), or platinum catalyst such as 3-4% Pt in siliconeoil, (McGann NuSil Cat-50). The platinum catalyst may be present inabout 0.01 to about 3 wt %, or about 0.02 to about 1 wt %, or about 0.03to 0.5 wt % compared to the total weight of the first part of theunfilled composition. Especially when the reactive groups consist onlyof silanol moieties, acidic or mildly basic conditions will result incondensation and curing. Organopolysiloxanes carrying reactive silanolgroups may be condensed with multifunctional organosiloxanes or silaneswhich condense with the silanol groups. Especially suitablefunctionalities for such condensation are acyloxy, amine, oxime andalkoxy reactive groups. Such condensations are often catalyzed bytitanates and carboxylic acid salts of zinc, iron and tin.Organopolysiloxanes and organosiloxanes of silanes carrying reactivehalogen atoms bonded to silicon, for example chlorine atoms, can becured with moisture or by reaction with, for example dimethylaminesubstituted organopolysiloxanes, organosiloxanes or silanes.

Specific examples of compounds particularly useful in the practice ofthis invention include, in addition to the compounds described in theexamples, acetoxy terminated polydimethylsiloxane with a molecularweight of about 36,000; methyldiacetoxy terminated polydimethylsiloxanewith a molecular weight of about 36,000; chlorine terminatedpolydimethylsiloxane with a molecular weight of 425 to 600;dimethylamine terminated polydimethylsiloxane with a molecular weight ofabout 425 to about 600; ethoxy terminated polydimethylsiloxane with amolecular weight of from about 360 to 1200; vinyldimethyl terminatedpolydimethylsiloxane with a viscosity of from about 2 to about 1,000,000cs; vinylphenylmethyl terminated polydimethylsiloxane with a viscosityof from about 1,000 to about 100,000 cs; divinylmethyl terminatedpolydimethylsiloxane with a viscosity of from about 1,000 to about100,000 cs; vinyldimethyl terminated dimethyl siloxane-methyl-vinylsiloxane (0.3-0.4%) copolymer with a viscosity of from about 1,000 cs;vinyldimethyl terminated polydimethylsiloxane vinyl Q-resin dispersionwith a viscosity of from about 4,000 to about 70,000 cs; hydrogenterminated polydimethylsiloxane with a molecular weight of from about400 to about 10,000; aminopropyldimethyl terminated polydimethylsiloxanewith a molecular weight of from about 50 to about 2,000;aminobutyldimethyl terminated polydimethylsiloxane with a molecularweight of from about 50; carboxypropyldimethyl terminatedpolydimethylsiloxane with a molecular weight of from about 2500 to about3500; chlorodimethyl terminated polydimethylsiloxane with a molecularweight of from about 2500 to about 3500;dimethylsiloxane-methylvinylsiloxane copolymers with from about 1.0 toabout 20% of the vinyl comonomer having viscosities in the range of fromabout 250 to about 300,000 cs; dimethysiloxane copolymers withacryloxypropylmethyl siloxane, aminopropylmethyl siloxane,(chloromethylphenylethyl)methyl siloxane, chloropropylmethyl siloxane,chloropropylmethyl siloxane (vinyldimethylsiloxy terminated),(methacryloxy-propyl)methyl siloxane, octyloxymethyl siloxane; branchedpolydimethylsiloxanes having 2 to 3 (T-structure) branch points withaminoalkyl, carboxypropyl, chloropropyl, glycidoxypropyl,mercaptopropyl, methacryloxypropyl and vinyl reactive groups at eachbranch point; branched polydimethylsiloxanes having 2 to 3 (T-structure)branch points with aminoalkyl, carboxypropyl, chloropropyl,glycidoxypropyl, mercaptopropyl, methacryloxypropyl and vinyl reactivegroups at each branch terminus; polymethylhydrosiloxanes havingmolecular weights from about 360 to about 5000; copolymers ofmethylhydrosiloxanes (from about 0.5 to about 60% by weight) withdimethylsiloxanes having molecular weights from about 900 to about63,000; copolymers of methylhydrosiloxane (from about 0.5 to about 50%by weight) with phenylmethylsiloxane having molecular weights from about1000 to about 2,000; and silanol and vinyldimethyl terminateddimethydiphenylsiloxane copolymers having from about 3 to about 25% byweight diphenylsiloxane groups. Many of these materials may be obtainedfrom United Chemical Technologies (UCT), Bristol, Pa.

The curable compositions of this invention and the compositions madeaccording to this invention may contain various additional ingredientssuch as flame retardants, corrosion inhibitors, antioxidants, UV lightstabilizers, fungicides and other biocides, fillers to enhance ordecrease refractive index, adjust density or other physical properties.Such additives or fillers also may be used to regulate or affect therate of extent of cure and crosslinking and affect the overall cost ofthe final composition. For example, the filler may include a submicronor nanoparticle silica powder. Due to the index matching limitations ofthe nanoparticle powder, these materials are available from 1.46 to 1.59refractive index range. In one objective, use of the index-matching gelimproves the return loss in a mechanical fiber splice. The silicaparticles may be used, e.g., as a rheology agent or to tune therefractive index of the cured composition.

In some embodiments, the submicron silica particles are non-aggregatedsilica particles to be incorporated in the liquid polymers andcopolymers are optionally surface modified with silane (also calledorganosilicon) coupling agents to improve their dispersibility in thepolymer matrix and, if required, to adjust the refractive index of thesurface of the silica particles so that it substantially matches therefractive index of the polymer medium. In some embodiments, the silicaparticles are submicron amorphous silica particles. In some embodiments,the silica particles have a submicron mean diameter. The index-matchingbase gel composition may include one or more submicron silica powders.The particle size of the silica gel, silica sol, fumed silica, or silicapowder is sub-micron, preferably less than 500 nanometers, less than 200nanometers, less than 150 nm, less than 100 nm, less than 50 nm, lessthan 25 nm, less than 10 nm in diameter. In some embodiments, the meandiameter of the silica particles is selected from 1-200 nm, 5-150 nm,10-100 nm, or 10-50 nm.

In some embodiments, the index-matching gel may include from 0-50 wt %,5-45 wt %, 10-40 wt %, or 25-35 wt % submicron silica particles. Theindex matching gel may further comprise various additives selected fromantioxidants, stabilizers, moisture scavengers, antimicrobials,fungicides, cure inhibitors, and tackifiers. The index matching gel mayfurther include one or more additives at from 0.001 wt % to 2 wt % ofthe gel composition.

The gel may include a variety of additives, including stabilizers andantioxidants such as hindered phenols (e.g., Irganox 1076, commerciallyavailable from BASF Corporation, Florham Park, N.J.) phosphites (e.g.,Irgafos™ 168, commercially available from BASF Corporation, FlorhamPark, N.J.), metal deactivators (e.g., Irganox™ D1024 from BASFCorporation, Florham Park, N.J.), and/or sulfides (e.g., Cyanox™ LTDP,commercially available from Cytec Industries Inc., Solvay Group,Woodland Park, N.J.) light stabilizers (e.g., Cyasorb™ UV-531,commercially available from Cytec Industries Inc., Solvay Group,Woodland Park, N.J. and/or flame retardants such as halogenatedparaffins (e.g., Bromoklor™ 50, commercially available from Ferro Corp.of Hammond, Ind., or Dover Chemical Corp., Dover Ohio), and/orphosphorous containing organic compounds (e.g., Fyrol™ PCF (tris(2-chloroisopropyl)phosphate) and Phosflex™ 390 (isodecyl diphenylphosphate), both commercially available from ICL Industrial Products)and/or acid scavengers (e.g., DHT-4A™, commercially available from KyowaChemical Industry Co. Ltd through Mitsui & Co. of Cleveland, Ohio, andhydrotalcite). Other suitable additives include biocides, tackifiers andthe like described in “Additives for Plastics, Edition 1” published byD.A.T.A., Inc. and The International Plastics Selector, Inc., San Diego,Calif.

In some embodiments, the article on which, within which or around whichthe curable compositions of the invention are cured is primed with asilane coupling agent. Such coupling agent are well known in the art asbeing advantageous for improving the bonding of addition cure siliconesto substrates. These coupling agents include but are not limited totrichlorosilane, organochlorosilanes such as vinyltrichlorosilane andmethylvinyldichlorosilane, organosilane esters such as methyltriethoxyand methyltrimethoxy silanes, organofunctional silanes such asvinyltrimethoxysilane and vinyltriacetoxysilane, methacryl organosilanessuch as gamma-methacrloxypropyltrimethoxysilane, epoxy silanes such asbeta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and amino organosilanessuch as gamma-aminopropyltriethoxysilane, silane titanates and the like.Typically the coupling agent is mixed into a solvent, for example onewhich activates the coupling agent. The solution may be brushed onto thesubstrate or applied by other methods well known to those of averageskill in the art such as casting, dipping spraying and the like. Afterapplication the primer coated article is allowed to sit for at leastabout 30 minutes so that the solvent can evaporate and the silanehydrolysed by moisture in the air. Once the priming is completed thecurable compositions of the invention can be poured into on or aroundthe substrate and cured.

The term crosslink refers to a covalent bond formed by chemical reactionbetween two crosslinkable sites from which sites depend a total of threeor more molecular segments; or at least two covalent bonds, each formedby chemical reaction between two crosslinkable sites, attaching achemical moiety to at least two polymer chains such that the chemicalmoiety has at least three molecular segments depending therefrom.Typically the chemical moiety is the residue of a low molecular weightcompound or a low molecular weight oligomeric material containing atleast three crosslinkable sites. Specifically, the term crosslinkcontemplates both trifunctional (T-links) (that is crosslinks havingthree molecular segments depending therefrom) tetrafunctional (H-links)(that is crosslinks having four molecular segments depending therefrom)and higher functionality crosslinks.

Without being bound by theory it is believed that crosslinking byreaction of functionalized molecules, where the mole equivalent ratiosare far from the stoichiometric ranges needed to achieve a crosslinkedgel network having adequate physical properties, can result, not indesired inter-molecular closed loop formation, but in extensive linkingof chains to the cured organopolysiloxane gel structure by a very fewand often only one reactive site such that many of the chains formdangling “tails” from the three dimensional cured organopolysiloxanegel. Such dangling chains, although they do form part of the curedorganopolysiloxane gel and thus contribute to the curedorganopolysiloxane gel fraction (that fraction of the originalcomposition comprising organopolysiloxane and crosslinker renderedinsoluble by co-reaction), make no substantial contribution to importantmechanical properties of the cured organopolysiloxane gel. Thus we havediscovered that the cured organopolysiloxane gels prepared by themethods of this invention having similar hardness values as measured bya texture analyzer compared to those of soft cured organopolysiloxanegels prepared by the methods of the prior art unexpectedly exhibit muchhigher ultimate elongation and toughness properties with greater tensilestrength and can accept significant amounts of diluent withoutexhibiting syneresis especially under compression while stillmaintaining desirable levels of tack.

The index-matching gel exhibits self-healing properties when the fibersare withdrawn from the gel, e.g., from within the housing. Gel cohesionis stronger than gel adhesion to the surface of the fibers. Uponwithdrawal of the fibers immersed in and closely surrounded by the gel,the gel closes in on the void created by the fiber withdrawal, and thefibers exhibit little to no trace of the gel. In addition, the gel isnot drawn outwards by the fibers.

Self-healing means that the fiber passage in the gel re-closes after a125 micron optical fiber is withdrawn from the gel at atmosphericpressure. It is one objective to have the gel re-seal fully to close outthe external environment from the fiber-fiber interface space within theconnector-adaptor. It is another objective that the gel will self-healas evidenced by visual appearance. In embodiments, the indematching gelwill self-heal within 1 second, 2 seconds, 3 seconds, 4 seconds, 5seconds, 10 seconds, 20 seconds, 30 seconds, 45 seconds, or within oneminute of withdrawing the optical fiber from the gel.

It is one objective that the index-matching self-healing gel willself-heal meaning that the fiber passage substantially or completelydisappears such that is no longer identifiable and/or the gel ishomogeneous/consistent/undisturbed across the previous location of thefiber passage.

In one objective, the self-healing gel would re-seal to be liquid tight,for example, at atmospheric pressure, after 2, 3, 4, 5, 6, 7, 8, 9, 10,15, 20, 25, 30 or more cycles of insertion and withdrawal of an opticalfiber at ambient temperature. In a further objective, the index-matchinggel will be able to self-heal after from 2-200 cycles, 5-100 cycles,10-50 cycles, or at least 10 re-close cycles, per GR326 compliance lifetesting.

In some embodiments, the self-healing gel would re-seal to excludeairborne dust, particulates, and aerosolized liquids. However, in someembodiments, the index-matching gels may not fully prevent diffusion ofvapor or gas phase substances.

In a further objective, the gel self-heals at least along the outside orexternal environment face to prevent contamination of the fiber-fiberinterface. In some embodiments, the re-sealing gel deposit isnon-homogenous, either due to a degree of cure gradient or due to amulti-gel layered deposit, there may be re-close difference along thefull length.

It is another objective that the gel self-heals along the entire lengthof the void created by withdrawal of the fiber such that the re-sealinggel deposit in the connector/adaptor is completely homogenous. Fullyre-closing along the length of the fiber aids the cleaning function ofthe gel, serving to wipe off any residual contamination that may be onthe fiber.

It is another objective that the self-healing index-matching gelre-close or self-heal after the fiber has been in the gel for a certainperiod of time selected from 10 minutes, 30 minutes, 1 hour, 1 day, 1week, 1 month, 3 months, 6 months, 12 months, 18 months, 24 months, 30months, 24 months, 36 months, or 48 months, and then removed. It is oneobjective that the gel be able to self-heal and re-close after anypractical life duration including several years.

It is another objective that the self-healing index-matching gel is acured polysiloxane gel that does not exhibit tracking or tear-out of thegel for at least 6 cycles, at least 8 cycles, or at least 12 cyclesafter inserting and withdrawing an optical fiber from the curedpolysiloxane gel. The Refractive Index of the index-matching gel may beobtained at 589 nanometer(nm) wavelength(a.k.a. “the Sodium D line”, or“nD”) with a refractometer using the method of ASTM D-1218 at a fixedtemperature of 25.0° C. Other wavelengths for measuring refractive-indexmay be selected from 402, 633, 980, and/or 1550 nm. As previouslymentioned, silicones have a refractive index range of 1.38-1.60. Therefractive index of the index-matching composition is preferably aboutthe same (+/10%) as that of the optical fiber. In one aspect, theindex-matching gel exhibits a refractive index of about 1.46+/−0.1,1.46+/−0.05, or 1.46+/−0.01 by ASTM D-1218. The index-matching gel maybe a silicone curing gel that exhibits good index match to the glassfiber, high optical clarity, and low absorption loss.

The cone penetration parameters may be measured according to ASTM D-217,as disclosed in U.S. Pat. No. 5,357,057 to Debbaut et al., which isincorporated herein by reference in its entirety. Cone penetration(“CP”) values may range from about 70 (10⁻¹ millimeter) to about 400(10⁻¹ millimeter). Harder gels may generally have CP values from about70 (10⁻¹ millimeter) to about 120 (10⁻¹ millimeter). Softer gels maygenerally have CP values from about 200 (10⁻¹ millimeter) to about 400(10⁻¹ millimeter), with particularly preferred range of from about 250(10⁻¹ millimeter) to about 375 (10⁻¹ millimeter). For a particularmaterials system, a relationship between CP and Voland gram hardness, orgram hardness as measured by another texture analyzer, can be developedas proposed in U.S. Pat. No. 4,852,646 to Dittmer et al. In someaspects, the cured or crosslinked composition will have a conepenetration according to ASTM No. D217-68 of about 100 to about 350(mm⁻¹).

In some embodiments, the gel may have an elongation, as measured by ASTMD638, of at least 55%. According to some embodiments, the elongation isat least 100%. In some embodiments, the gel may have an ultimateelongation in accordance with ASTM D638 of greater than about 200%. Inother embodiments, index-matching gels in accordance with the principlesof the present disclosure have ultimate elongations of at least 200percent, or at least 400 percent, or at least 500 percent, or at least1,000 percent.

In certain embodiments, the gel composition has less than 20% bleed outover a period of time when the gel is under compression of 50 kPa (0.5atm) or 120 kPa (1.2 atm) at 60° C. The weight of the gel sample isrecorded before and after the pressure has been applied. In certainembodiments, extender bleed out is measured on a wire mesh, wherein theoil loss may exit the gel through the mesh. Typically, gel samplesshould be 3 mm±0.5 mm thick and have a diameter of 14 mm±0.5 mm, andthree samples should be tested from each gel. The gel sample is placedinto a cylindrical hole/tube resting on a fine and rough screen, whichgives enough support to hold the gel but in the meantime allows the oilto separate from the gel. Pressure is applied to the gel by placing aweight on top of a piston (which prevents the gel from creeping out ofthe hole. Typically, approximately 50 kPa (0.5 atm) or 120 kPa (1.2 atm)of pressure is placed on the gel sample. Then, the sample is placed inan oven at 60° C. After 24 hours, the sample is removed from the oven toclean the surface oil and weigh the gel. The sample is then returned tothe oven. Weight measurements are taken every 24 hours untilstabilization has occurred (e.g., when 5 weight measurements areconstant).

In some embodiments, the gel has less than 20%, 15%, 10%, or 5% extenderbleed out over the period of time. In certain embodiments, the oil lossis measured at 200 hours, 400 hours, 600 hours, 800 hours, 1000 hours,1200 hours, or 1440 hours (60 days).

The tack and stress relaxation may be read from the stress curvegenerated when the XT.RA Dimension version 2.3 software automaticallytraces the force versus time curve experienced by the load cell when thepenetration speed is 2.0 mm/second and the probe is forced into the gela penetration distance of about 4.0 mm. The probe is held at 4.0 mmpenetration for 1 minute and withdrawn at a speed of 2.00millimeters/second. The stress relaxation is the ratio of the initialforce (F_(i)) resisting the probe at the pre-set penetration depth minusthe force resisting the probe (F_(f)) after 1 minute divided by theinitial force expressed as a percentage. That is, percent stressrelaxation is equal to ((F_(i)−F_(f))/F_(i))×100% where F_(i) and F_(f)are in grams. In other words, the stress relaxation is the ratio of theinitial force minus the force after 1 minute over the initial force. Itmay be considered to be a measure of the ability of the gel to relax anyinduced compression placed on the gel. The tack may be considered to bethe amount of force in grams resistance on the probe as it is pulled outof the gel when the probe is withdrawn at a speed of 2.0millimeters/second from the preset penetration depth.

Hardness as measured by a texture analyzer, or Voland hardness, andother properties of the gels may be measured using a TextureTechnologies Texture Analyzer TA-XT2 commercially available from TextureTechnologies Corp. of Scarsdale, N.Y., or like texture analyzer machinessuch as formerly produced by Voland/Stevens such as Texture AnalyzerModel LFRA. The texture analyzer is equipped with a one-fourth inch(0.25 inch or 6.35 mm) stainless steel ball probe, a 5 gram trigger, andhaving a 100 g or a 1000 g load cell to measure force. For measuring thehardness of the gel materials of the present invention a 20 ml glassscintillating vial containing 10 grams of gel is placed in the TextureAnalyzer and the stainless steel ball probe is forced into the gel at aspeed of 0.2 mm/min to a penetration distance of 4.0 mm. The hardnessvalue of the gel is the force in grams required to force the ball probeat that speed to penetrate of deform the surface of the gel thespecified 4.0 mm. The Voland hardness, or hardness as measured by atexture analyzer, or Voland hardness, of a given sample may be directlycorrelated to the ASTM D217 cone penetration hardness and the procedureand a correlation is shown in FIG. 3 of U.S. Pat. No. 4,852,646, patentapplication Ser. No. 07/063,552 (Dittmer and Dubrow) filed Jun. 16,1987. According to some embodiments, the cured index-matching gel has ahardness, as measured by a texture analyzer, or Voland hardness ofbetween about 1 grams and 100 grams force, or between 1 g to 50 g force,between 2 g to 40 g force, between 5 g to 30 g force, or between 10 g to20 g force.

The estimation of Mc, Average Molecular Weight between crosslinks, maybe performed by the following method. A disc-shaped specimen of thecured organopolysiloxane gel composition (approximately 2.5 cm radiusand 0.1 to 0.2 cm thick) is prepared and soaked in toluene (or otherswelling agent for the cured organopolysiloxane gel and suitableextractant for the soluble components of the composition) for 2 to 3days, periodically replenishing the toluene or other extractant (forexample, twice a day). The swollen organopolysiloxane gel is then driedin a vacuum oven at about 60°-80° C. (or other suitable temperature) for24 hours to remove the extractant. If necessary an intermediate exchangeof the extractant with, for example, acetone may be used to facilitateand speed up removal of the extractant. This dried organopolysiloxanegel is then placed between parallel plates in a Rheometrics MechanicalSpectrometer (RMS) at 25°. The plateau modulus Gp (in dynes per cm²) isthen determined using a frequency rate of oscillation of the plates of 1to 100 rad per second. From this modulus value a Mc can be calculatedfrom the relation:

M _(c)=(d×R×T)/G _(p)

where d is the density (in g per cm³) of the extractedorganopolysiloxane gel, R is the gas constant and T is the absolutetemperature.

In the case of gels which contain fillers, the contribution of thefiller to the modulus must be taken into account. In this instance themeasured modulus (G_(f)) is related to the modulus by:

(G _(f))=GP(1+2.5ϕ+14.1ϕ²)

where G_(p) is the modulus contribution from the network alone in theabsence of filler and .phi. is the volume fraction of the filler in thediluent free gel. The weight fraction of filler can be determined byThermo-gravimetric analysis (TGA): this involves pyrolysing thecrosslinked polymer composition and determining the residual weight ofthe filler. The crosslink density may be determined as follows thenumber of network segments per unit volume v is related to Mc by thefollowing relation:

C=2/(M _(c) ×F)

If F is not known independently (through, for example, knowledge of thereactive ingredients from which the gel was produced) it is assumed tobe 3. Unreacted reactive groups in a cured gel composition may beidentified and their concentration estimate using a number of techniquessuch as infra-red absorption and nuclear magnetic resonance (NMR). Atpresent the preferred method is solid state (usually proton) NMR. Thechemical shifts observed can be used to identify the type of functionalgroups present; once the relaxation times are determined, their numbercan also be determined.

Comparative Example 1

Nyogel™ OC-431A-LVP is an index matching thixotropic grease for fiberoptic connectors marketed by W. F. Nye, Inc. (New Bedford, Mass.). TheComparative Example 1 gel consists of 90% by weight silicone fluid and10% fume silica thickener with 0.04% of 2,6-di-tert-butyl-p-cresol.Comparative Example 1 gel exhibits a refractive index at 589.3 nm of1.46 by ASTM D-1218, viscosity at 25° C. of 11000 poises, and conepenetration of 243 (10⁻¹ millimeter) by ASTM D-217. However, ComparativeExample 1 gel exhibits tracking following withdrawal of optical fiberafter the sixth cycle, as shown in FIG. 15.

Example 2

This procedure describes in general terms the method used to make theformulations of the remaining examples, which comprise examples of theinvention. They are each composed of two parts comprising variousingredients. All components are parts by weight. Unless otherwisespecified, the ratio of part 1 and part 2 is 1:1; however to obtainvarious properties in the cured organopolysiloxane gels this ratio maybe varied.

The components may be weighed on an analytical balance (accuracy+−0.01g) then mixed with an overhead stirrer equipped with a propeller blade.The blended mixture may then cast into a 6″×6″×0.125″ mold and cured at120° C. for four hours in an air circulating oven. Three 20 mlscintillation vials may be filled with 12 g each of the mixture andcured under the same conditions. Cured organopolysiloxane gels ofdifferent hardnesses may prepared by varying the ratio of the tworeactants (Table 1).

The hardness may be determined for each formulation using a TextureTechnologies Texture Analyzer by the method provided herein above.Elongation may be measured using the procedures described in ASTM D419where tensile bars are die cut from the molded slabs and elongationmeasured.

Part A:

35.000% organopolysiloxane −80,000 CSt divinyl terminated PDMS (such asAndisil VS 80K from AB Specialty Silicones),

64.917% non-reactivediluent-2,2,4,4,6,6-hexamethyl-8,8-diphenyl-cyclotetrasiloxane (AlfaChemistry, US, ACM1693443), 0.083% Pt catalyst complex, Platinum 0-1,3divinyl-1,1,3,3-tetramethyldisiloxane complex solution in vinylterminated PDMS

Part B:

34.894% organopolysiloxane 80,000 CSt divinyl terminated PDMS (such asAndisil VS 80K from AB Specialty Silicones),

64.977% non-reactive diluent2,2,4,4,6,6-hexamethyl-8,8-diphenyl-cyclotetrasiloxane (Alfa Chemistry,US, ACM1693443),

0.052% Tetrakis (dimethylsiloxy) silane,

0.078% Phenyl Tris(dimethylsiloxy) silane

The ingredients are weighed sequentially and then mixed as describedabove. The formulations may be poured into scintillation vials and curedto provide specimens for the hardness and stress relaxation measurementsand also into a slab mold and cured to provide specimens for the othertests.

Example 3

Part A:

30.000% 80,000 CSt divinyl terminated PDMS dimethylpolysiloxane (AndisilVS 80,000 from AB Specialty Silicones),

15.000% 165,000 CSt divinyl terminated PDMS dimethylpolysiloxane(Andisil VS 165,000 from AB Specialty Silicones),

15.000% MV 2000 (mono functional vinyl dimethylpolysiloxane diluent fromAB Specialty Silicones),

39.917% 2,2,4,4,6,6-hexamethyl-8,8-diphenyl-cyclotetrasiloxanediluent(Alfa Chemistry, US, ACM1693443),

0.083% Pt catalyst complex, Platinum 0-1,3divinyl-1,1,3,3-tetramethyldisiloxane complex solution in vinylterminated PDMS.

Part B:

29.894% divinyl terminated PDMS Andisil VS 80,000,

15.000% divinyl terminated PDMS Andisil VS 165,000,

15.000% mono functional vinyl diluent (MV 2000 from AB SpecialtySilicones),

39.977% 2,2,4,4,6,6-hexamethyl-8,8-diphenyl-cyclotetrasiloxane(AlfaChemistry, US, ACM1693443),

0.080% Tetrakis (dimethylsiloxy) silane,

0.0508% Phenyl Tris(dimethylsiloxy) silane.

The ingredients are weighed sequentially and then mixed as describedabove. The formulations may be poured into scintillation vials and curedto provide specimens for the hardness and stress relaxation measurementsand also into a slab mold and cured to provide specimens for the othertests.

Example 4

Part A: 45.000% 80,000 CSt divinyl terminated PDMS (Andisil VS 80K fromAB Specialty Silicones),

10.000% divinyl terminated PDMS Andisil VS 165,000,

5.000% mono functional vinyl diluent (MV 2000 from AB SpecialtySilicones),

39.917% 1,3,5-triphenyltrimethylcyclotrisiloxane, CAS RN 546-45-2,available from GELEST, Morrisville, Pa., Product Code: SIT8705.0

0.083% Pt catalyst complex, Platinum 0-1,3divinyl-1,1,3,3-tetramethyldisiloxane complex solution in vinylterminated PDMS.

Part B:

44.894% divinyl terminated PDMS Andisil VS 80,000,

10.000% divinyl terminated PDMS Andisil VS 165,000,

5.000% mono functional vinyl diluent (MV 2000 from AB SpecialtySilicones),

39.977% 1,3,5-triphenyltrimethylcyclotrisiloxane, CAS RN 546-45-2,available from GELEST, Morrisville, Pa., Product Code: SIT8705.0,

0.0608% Tetrakis (dimethylsiloxy) silane,

0.072% Phenyl Tris(dimethysiloxy) silane

The ingredients are weighed sequentially and then mixed as describedabove. The formulations may be poured into scintillation vials and curedto provide specimens for the hardness and stress relaxation measurementsand also into a slab mold and cured to provide specimens for the othertests.

Example 5

Part A:

45.000% 80,000 CSt divinyl terminated PDMS (Andisil VS 80K from ABSpecialty Silicones),

10.000% divinyl terminated PDMS Andisil VS 165,000,

5.000% mono functional vinyl diluent (MV 2000 from AB SpecialtySilicones),

39.917% 1,1-diphenyltetramethylcyclotrisiloxane, CAS RN 1693-51-2,available from ChemTik, Berlin, Germany, Product Code: CTK4D3277

0.083% Pt catalyst complex, Platinum 0-1,3divinyl-1,1,3,3-tetramethyldisiloxane complex solution in vinylterminated PDMS.

Part B:

44.894% divinyl terminated PDMS Andisil VS 80,000,

10.000% divinyl terminated PDMS Andisil VS 165,000,

5.000% mono functional vinyl diluent (MV 2000 from AB SpecialtySilicones),

39.977% 1,1-diphenyltetramethylcyclotrisiloxane, CAS RN 1693-51-2,available from ChemTik, Berlin, Germany, Product Code: CTK4D3277,

0.0608% Tetrakis (dimethylsiloxy) silane,

0.072% Phenyl Tris(dimethysiloxy) silane

The ingredients are weighed sequentially and then mixed as describedabove. The formulations may be poured into scintillation vials and curedto provide specimens for the hardness and stress relaxation measurementsand also into a slab mold and cured to provide specimens for the othertests.

Example 6

A gel was formulated without non-reactive diluent in order to firstassess and tune self-healing and self-cleaning characteristics.

Part A:

98.517% 5,000 CSt divinyl terminated PDMS (Andisil VS 5K from ABSpecialty Silicones),

0.4% Dynasylan 40 (ethyl polysilicate, 40-42% silicon hydroxide)CTK4D3277

0.083% Pt catalyst complex, Platinum 0-1,3divinyl-1,1,3,3-tetramethyldisiloxane complex solution in vinylterminated PDMS.

Part B:

97.36% divinyl terminated PDMS (Andisil VS 5,000: CTK4D3277),

0.30% Tetrakis (dimethylsiloxy) silane,

2.34% Hydride terminated polydimethylsiloxane, 2-3 cSt, 0.5 wt % hydride

The ingredients are weighed sequentially and then mixed as describedabove. The formulations may be poured into scintillation vials and curedto provide specimens for the hardness and stress relaxation measurementsand also into a slab mold and cured to provide specimens for the othertests.

The gel formulations being used can hold a quantity of soluble diluent,without significant bleed-out or gel property change. The high index ofrefraction non-reactive diluents are used to adjust the index ofrefraction of the gel to the desired level.

Example 7

Discrete product applications may require a differing levels of“self-healing” and “self-cleaning” characteristic, depending upongeometry, fiber diameter, gel reservoir geometry, and environment. Theability to tune these properties by adjusting the Part A to Part B ratiowas investigated.

Self-healing gels that do not exhibit tracking or tear-out uponinsertion and withdrawal of an optical fiber were desirable. “Tracking”and “Tear-Out” observations were made using video imaging using amounted gel substrate on a ThorLabs optical bench stage and a mounted asquare cleaved optical fiber on an aligned ThorLabs optical bench stage.The bench geometry allowed the square cleaved optical fiber to be movedin and out of the gel under observation. For example, the optical fiberwas inserted and withdrawn from the sample gel multiple times and thegel characteristics were recorded by video photography. For example, onecycle of insertion and withdrawal of the fiber from the cured gel wasperformed every minute for at least 12 cycles. Initial work performedwas performed with the gel mounted in the Fiber Alignment Housing, laterwork performed with gel mounted between two glass slides.

With the gel mounted in Fiber Alignment Housings, the gel was in apossible geometry of use, but the performance of the gel below thesurface was difficult to observe. For example, when viewed in the FiberAlignment Housing, typical gel performance appears in FIGS. 14 and 15.Prior art commercial cross-linked gels, for example, NYOGEL® OCK-451A(Nye Lubricants, Inc., Fairhaven Mass.), can achieve index match, andre-seal, but one problem is they may start to exhibit tear-out after anumber of cycles. An example is shown in FIG. 14, prior art cross-linkedgel exhibiting tear-out as evidenced by traces of gel visually apparentalong the withdrawn optical fiber.

Prior art commercial thixotropic greases, for example NYOGEL® OC431ALVP, can exhibit good index-match, with good fiber release, but mayexhibit another problem in that they fail to self-heal as exhibited bytracking or passage evident after a number of cycles. For example, asshown in FIG. 15, prior art thixotropic grease exhibits tracking afterwithdrawal of the optical fiber, thus fails to adequately self-heal.

The protocol was modified to improve observation of gel behavior. Withgel mounted between two glass slides, the gel behavior below thepenetration surface was able to be observed. When viewed between twoglass slides, the gel behavior appears as shown in FIG. 16, in which theprior art thixotropic grease exhibits tracking similar to FIG. 15. Inaddition, although the material does not tear out, the fiber is coatedwith grease.

The gel according to Example 6 was prepared using various ratios of PartA to Part B. As shown in the Table 1, repeated insertion and withdrawalof optical fiber from cured gels at ambient room temperature for atleast 12 cycles resulted in no tracking and no tear-out of the gel.

TABLE 1 Tracking and Tear-out observations for Cured Gels of Example 6Part A:Part B FIG. Tracking Tear-out example 6.1 17A None observed Noneobserved 1.00:1.04 Dimple observed in gel at exit point. example 6.2 17BNone observed “Draw-Out” 1.04:1.00 Dimple observed in observed, thatsnaps gel at exit point. back to gel matrix in 2-3 seconds. example 6.317C None observed “Draw-Out” 1.06:1.00 Dimple observed in observed, thatsnaps gel at exit point, back to gel matrix in 10-12 seconds.

Example 8

The polysiloxane gels of the disclosure were subjected to self-cleaningevaluation. Dust selection and evaluation method is described in thisexample. Many types of particulate contamination and dust can adverselyaffect optical connector performance. Many tests exist to assess theperformance of product after exposure to a dust bearing environment. Onesuch test is identified in Telcordia GR-326-CORE “Generic Requirementsfor Singlemode Optical Connectors and Jumper Assemblies”, section4.4.4.1 “Dust Test”, which specifies the use of ISO 12103-1 “Test dustfor filter evaluation—Part 1: Arizona test dust”, type A2 “fine testdust” was used for this evaluation. For this evaluation, an opticalfiber was coated with ISO 12103-1 type A2 “fine test dust” and thenobserved the action taken on the dust by the gel. Results are shown inFIGS. 18A-D. FIG. 18A shows an initial image where the fiber is coatedwith dust. FIG. 18B shows the fiber after insertion to the cured gelaccording to example 6.1 using a Part A:Part B ratio of 1.00:1.04; dustremoval from optical fiber is observed in the marked region along thefiber and dust transfer to the gel face is observed in the gel at thecircled region. Therefore, the gel according to example 6.1 was observedto be self-cleaning.

For comparison, prior art thixotropic grease is shown prior to fiberinsertion in FIG. 18C, with dust shown along the optical fiber. Afterfiber is inserted and withdrawn from the prior art, dust still appearson the optical fiber observed in the horizontal lines along the fiber atthe marked region. Dust was transferred to the grease, but was depositedalong the circled track region. Therefore, the gel according to example6.1 was observed to be self-cleaning, whereas prior art thixotropicgrease exhibited tracking and insufficient self-cleaning properties.

1. An optical fiber alignment system comprising: an alignment devicedefining a fiber insertion axis extending between first and second endsof the alignment device, the alignment device also defining a fiberalignment region positioned along the fiber insertion axis; and a curedrefractive index-matching gel composition positioned within the fiberalignment region, wherein an optical fiber to be aligned penetratesthrough the gel, wherein the cured refractive index-matching gelcomposition comprises a crosslinked polysiloxane, and optionally anonreactive polysiloxane diluent.
 2. The optical fiber alignment systemof claim 1, wherein the cured refractive index-matching gel compositioncomprises a crosslinked polysiloxane, and a nonreactive polysiloxanediluent, wherein the refractive index of the diluent is higher than therefractive index of the crosslinked polysiloxane.
 3. The optical fiberalignment system of claim 1, wherein the cured refractive index-matchinggel composition is self-healing as indicated by re-seal to be liquidtight upon water submersion after at least 10 seconds following removalof a 125 micron optical fiber from the gel composition within aconnector.
 4. The optical fiber alignment system of claim 1, wherein thecrosslinked polysiloxane is prepared from a polysiloxane compositioncomprising a first reactive polysiloxane component, and a secondreactive component capable of reacting with and curing the firstcomponent.
 5. The optical fiber alignment system of claim 4, wherein thefirst reactive polysiloxane component has at least two reactive groups.6. The optical fiber alignment system of claim 5, wherein the firstreactive polysiloxane component is selected from one or more of thegroup consisting of hydroxy-, alkoxy-, acyloxy-, amino-, oxime-,hydrogen- and vinyl-terminated polydimethylsiloxanes, and dihydroxy-,diacyloxy-, diamino-, dioxime-, dialkoxy-, dihydrogen- anddivinyl-terminated polydimethylsiloxanes and hydroxy-, alkoxy-,acyloxy-, amino-, oxime-, hydrogen- and vinyl-dimethyl and dihydroxy-,diacyloxy-, diamino-, dioxime-, dialkoxy-, dihydrogen- anddivinyl-terminated dimethylsiloxane copolymers with diphenyl siloxanes.7. The optical fiber alignment system of claim 4, wherein the secondreactive component has at least three reactive groups, or at least fourreactive groups.
 8. The optical fiber alignment system of claim 7,wherein the second reactive component is selected from the groupconsisting of tetrakis(dimethylsiloxy) silane,methyltris(dimethylsiloxy)silane, phenyl-tris(dimethylsiloxy)silane,tetraethoxysilane, tetramethoxysilane, phenyl triethoxysilane, methyltriethoxysilane, phenyl triacetoxysilane, 1,3,5-trimethyltrivinylcyclotrisiloxane, 1,3,5,7-tetramethyltetravinyl cyclotetrasiloxane, and1,3,5,7-tetra-methylcyclotetrasiloxane.
 9. The optical fiber alignmentsystem of claim 1, wherein the cured polysiloxane gel does not exhibittracking or tear-out of the gel for at least 6 cycles, at least 8cycles, or at least 12 cycles after inserting and withdrawing an opticalfiber from the cured polysiloxane gel.
 10. The optical fiber alignmentsystem of claim 9, wherein the nonreactive polysiloxane diluentcomprises a cyclosiloxane having at least one phenyl substituent,optionally wherein the diluent is selected from the group consisting ofa diphenyl cyclotrisiloxane (D3), triphenyl cyclotrisiloxane (D3),diphenyl cyclotetrasiloxane (D4), tetraphenyl cyclotetrasiloxane (D4),hexaphenyl cyclotetrasiloxane (D4), diphenyl cyclopentasiloxane (D5),tetraphenyl cyclopentasiloxane (D5), hexaphenyl cyclopentasiloxane (D5),diphenyl cyclohexasiloxane (D6), tetraphenyl cyclohexasiloxane (D6),hexaphenyl cyclohexasiloxane (D6), diphenyl cycloheptasiloxane(D7),tetra phenyl cycloheptasiloxane(D7), and hexaphenylcycloheptasiloxane(D7).
 11. The optical fiber alignment system of claim10, wherein the nonreactive polysiloxane diluent is selected from thegroup consisting of 1,1-diphenyltetramethylcyclotrisiloxane,1,3,5-triphenyltrimethylcyclotrisiloxane,2,2,4,4,6,6-hexamethyl-8,8-diphenyl-cyclotetrasiloxane,octamethyldiphenyl-cyclopentasiloxane, decamethyl diphenylcyclohexasiloxane, tetramethyltetraphenyl-cyclotetrasiloxane, andhexamethyl tetraphenyl-cyclopentasiloxane.
 12. The optical fiberalignment system of claim 1, wherein the crosslinked polysiloxane has anaverage molecular weight between crosslinks of at least 15,000.
 13. Theoptical fiber alignment system of claim 12, wherein the crosslinkedpolysiloxane has an average molecular weight between crosslinks of atleast 20,000.
 14. The optical fiber alignment system of claim 1, whereinthe gel composition comprises 40% up to about 90% by weight of thenonreactive polysiloxane diluent based on the combined weights of thecrosslinked polysiloxane and the nonreactive polysiloxane diluent. 15.The optical fiber alignment system of claim 4, wherein the polysiloxanecomposition further comprises one or more additives selected from thegroup consisting of catalysts, antioxidants, moisture scavengers,antimicrobials, flame retardants, corrosion inhibitors, UV lightstabilizers, fungicides, cure inhibitors, tackifiers, and nanoparticles.16. The optical fiber alignment system of claim 15, wherein thenanoparticles are selected from amorphous silica particles having meandiameter in the range of from 1 nm to no more than 500 nm.
 17. Theoptical fiber alignment system of claim 1, wherein the refractiveindex-matching polymer gel composition exhibits i. a hardness asmeasured by a texture analyzer, or Voland hardness, is in the range offrom 1 g to 50 g; ii. an ultimate elongation of at least about 100%; andiii. a refractive index in the range of from 1.31 to 1.60 at 1550 nm byASTM D-1218.
 18. The optical fiber alignment system of claim 17, whereinthe refractive index-matching polymer gel composition exhibits i. ahardness as measured by a texture analyzer, or Voland hardness, is inthe range of from 5 g to 30 g; ii. an ultimate elongation of at leastabout 400%; and iii. a refractive index in the range of from 1.40 to1.48 at 1550 nm by ASTM D-1218.
 19. The optical fiber alignment systemof claim 1, wherein the cured refractive index-matching gel compositionis self-healing as indicated by re-seal to be liquid tight upon watersubmersion after at least 10 seconds following removal of a 125 micronoptical fiber from the gel composition within a connector.
 20. Theoptical fiber alignment system of claim 1, wherein the fiber alignmentregion defines an alignment groove and a cantilever arm to axially alignthe optical fibers in the alignment groove.
 21. A cured refractiveindex-matching polymer gel composition comprising a crosslinkedpolysiloxane polymer, and optionally a nonreactive diluent, wherein therefractive index of the diluent is higher than the refractive index ofthe crosslinked polymer, wherein the cured polysiloxane polymer gel doesnot exhibit tracking or tear-out of the gel for at least 12 cycles afterinserting and withdrawing an optical fiber from the gel.
 22. The curedrefractive index-matching polymer gel composition of claim 21, whereinthe cured refractive index-matching gel composition is prepared from atwo-part composition comprising a part A and a part B, wherein part Aand part B are mixed in a ratio of from about 2:1 to 1:2; 1.5:1 to1:1.5, 1.1:1 to 1:1.1, or 1.05:1 to 1:1.05 part A:part B and cured. 23.A method for preparing a crosslinked organopolysiloxane gel whichcomprises reacting together a composition comprising: a) anorganopolysiloxane containing first reactive groups; and b) at least onecompound containing second reactive groups, wherein said second reactivegroups in the compound being capable of reacting with said firstreactive groups in the organopolysiloxane, and c) optionally anon-reactive polysiloxane diluent.
 24. The method of claim 23, whereinthe non-reactive polysiloxane diluent is inert to said first and saidsecond reactive groups, in an amount of from at least about 40% byweight to about 95% by weight of the combined weights of said diluent,said organopolysiloxane, and said compound, optionally wherein the inertdiluent is a cyclopolysiloxane having a refractive index higher than theorganopolysiloxane wherein the cyclopolysiloxane is selected from adiphenyl cyclotrisiloxane(D3); triphenyl cyclotrisiloxane (D3), diphenylcyclotetrasiloxane (D4), tetraphenyl cyclotetrasiloxane (D4), hexaphenylcyclotetrasiloxane (D4); methyl cyclopentasiloxane (D5), diphenylcyclopentasiloxane (D5), tetraphenyl cyclopentasiloxane (D5), hexaphenylcyclopentasiloxane (D5); methyl cyclohexasiloxane (D6), diphenylcyclohexasiloxane (D6), tetraphenyl cyclohexasiloxane (D6), hexaphenylcyclohexasiloxane (D6); diphenyl cycloheptasiloxane(D7), or a mixturethereof.
 25. The method of claim 24, wherein the cyclopolysiloxane isselected from the group consisting of1,1-diphenyltetramethylcyclotrisiloxane,1,3,5-triphenyltrimethylcyclotrisiloxane,2,2,4,4,6,6-hexamethyl-8,8-diphenyl-cyclotetrasiloxane,octamethyldiphenyl-cyclopentasiloxane, decamethyl diphenylcyclohexasiloxane, tetramethyltetraphenyl-cyclotetrasiloxane, andhexamethyl tetraphenyl-cyclopentasiloxane.